Is a self-employed dental hygienist's income subject to self-employment tax?

Yes, with no special carve-out. A hygienist who contracts as a per-diem or temp provider across multiple dental offices, a hygiene staffing platform, or a genuinely independent public-health practice reports the year's 1099-NEC income as Schedule C gross receipts and pays the full 15.3% self-employment tax (12.4% Social Security up to the annual wage base plus 2.9% Medicare) on 92.35% of net profit, the same as any other self-employed contractor. Whether the work is also a Specified Service Trade or Business (SSTB) for the separate §199A/QBI deduction — it generally is, see below — doesn't change the self-employment tax calculation at all; those are two independent parts of the return.

Is dental hygiene a Specified Service Trade or Business (SSTB) for the QBI deduction?

On a fairly clean reading of the regulation, yes — a cleaner call than some other licensed, patient-facing trades get. Treas. Reg. §1.199A-5(b)(2)(ii) defines the health field as 'the provision of medical services by individuals such as physicians, pharmacists, nurses, dentists, veterinarians, physical therapists, psychologists, and other similar healthcare professionals performing services in their capacity as such.' A dental hygienist isn't named in that list by title, but the work itself sits well inside it: performing a prophylaxis, scaling and root planing, periodontal charting and assessment, applying sealants and fluoride varnish, taking and interpreting radiographs, and — in most states — administering local anesthesia or nitrous oxide, all directly to a patient. That's substantively closer to the regulation's own Example 1 (§1.199A-5(b)(3)(i)), where a pharmacist 'performing inoculations' — a needle procedure on a patient — is held squarely in the health field, than to Example 4's lab-technical staff, who have no patient contact and 'do not diagnose, treat, or manage any aspect of patient care.' A hygienist exercises real clinical judgment (periodontal assessment, what a patient needs to hear about their own oral health) that a pure specimen-collection role doesn't. No IRS example names hygienists specifically, so treat this as reasoned analysis rather than a ruling on point, and get it confirmed in writing by an EA or CPA if your household income is near the threshold. Below that threshold ($201,750 single/head-of-household, $403,500 married filing jointly, per Rev. Proc. 2025-32), the SSTB question doesn't matter anyway — every filer still gets only the lesser of 20% of qualified business income or 20% of taxable income minus net capital gain under §199A(a)(2).

Why don't I have PPE and consumable supplies to deduct the way other self-employed health-adjacent workers do?

Because of how the work is structured, not because the expense category doesn't exist. A caregiver, phlebotomist, or massage therapist typically supplies their own gloves, masks, and consumables because there's no employer-like host site providing them. A per-diem hygienist working inside someone else's dental practice is different: the host office almost always supplies the chairside disposables — gloves, masks, prophy paste, saliva ejectors, barriers — as part of running its own clinical operation, the same way it supplies them to its own employees. Buying those yourself would usually be redundant and isn't the norm in this trade. What a hygienist typically does buy herself, and can deduct on Line 22, is different: her own hand-instrument kit (scalers, curettes, mirrors, probes) that she owns and carries from office to office — a real professional norm in this field, since instruments are set up to an individual clinician's preference — and magnification loupes with an LED headlight. Both are current-year Line 22 expenses under the de minimis safe harbor (Notice 2015-82) if each item costs $2,500 or less.

How does mileage work when I'm assigned to a different dental office almost every day?

It depends entirely on whether you've set up a qualifying home office — and without one, the answer is less favorable than it looks at first. IRS Publication 463 is direct about the general case: 'Unless you have a regular place of business, you can only deduct your transportation expenses to a temporary work location outside your metropolitan area.' A per-diem hygienist rotating through several dental offices in her own home metro area does not clear that bar just by lacking one fixed office — Publication 463's 'no regular place of business' exception only reaches temporary sites genuinely outside the metro area where she lives. Within her metro area, the plain commuting rule and the 'second job' rule govern instead for a hygienist with no other regular work location: the first drive of the day (home to the first office) and the last drive (an office back home) are nondeductible commuting, and only the drive between two offices on a day she works both — 'if you regularly work at two or more places in one day, whether or not for the same employer, you can deduct your transportation expenses of getting from one workplace to another' — is deductible business mileage. (A hygienist who does have one steady office she works regularly, plus occasional fill-in assignments elsewhere, gets a third route: Publication 463 also allows the deduction if 'you have one or more regular work locations away from your residence' — home-to-temporary-assignment mileage becomes deductible once a genuine regular work location exists, even without a qualifying home office.) The exception that actually unlocks full deductibility for a hygienist with no regular office at all is different: Publication 463 also allows the deduction 'if ... your residence is your principal place of business and you incur expenses going between the residence and another work location in the same trade or business, regardless of whether the work is temporary or permanent and regardless of the distance.' A hygienist who maintains a specific area of her home used regularly and exclusively to run the administrative side of her practice — confirming assignments, reconciling multiple 1099-NECs, maintaining her mileage log, ordering her own instruments — and has no other fixed location where she does that kind of administrative work (a dental office she's assigned to for the day isn't a location where she manages her own business) qualifies her home as her principal place of business under the administrative-activities rule in §280A(c)(1)'s flush language. Once that's true, every drive from home to any assignment is deductible under the exception above, regardless of distance — the correct legal route to the favorable result, not the 'no regular place of business' theory. Either way, use the standard mileage rate on Schedule C Line 9: 2026 has two rates because the IRS revised the rate mid-year — $0.725 per mile January 1 through June 30 (IR-2025-128), and $0.76 per mile from July 1, 2026 onward (IR-2026-29).

Can a hygienist deduct the cost of hygiene school and the National Board exam?

No — the associate or bachelor's degree program in dental hygiene, and the fee for the National Board Dental Hygiene Examination (NBDHE) and a regional or state clinical licensing exam, are a nondeductible personal capital expense, because they qualify you for a new trade or business. Treas. Reg. §1.162-5(b)(3)(i) places 'expenditures made by an individual for education which is part of a program of study being pursued by him which will lead to qualifying him in a new trade or business' in the nondeductible category — this applies even to someone who worked in an unrelated field first, because dental hygiene is its own credentialed trade requiring its own accredited program and licensing exams. Once licensed and working, the calculus flips: the regulation's own Example 3 (§1.162-5(b)(3)(ii)) confirms that a physician's two-week course 'reviewing new developments in several specialized fields of medicine' is deductible because it 'maintains or improves skills required by him in his trade or business and does not qualify him for a new trade or business.' The continuing-education hours most states require to renew an existing RDH license work the same way — deductible on Line 27a — because they maintain a credential you already hold rather than create a new one.

Can a per-diem dental hygienist take the home-office deduction?

More often than you'd guess, and this is the deduction that actually decides whether her mileage is fully deductible too — so it's worth getting the test right. §280A(c)(1)'s flush language extends 'principal place of business' to a home used 'for the administrative or management activities of any trade or business ... if there is no other fixed location of such trade or business where the taxpayer conducts substantial administrative or management activities.' The word 'substantial' modifies the *other* location, not the home's own admin work — the test isn't whether her home admin work is substantial, it's whether some other fixed place handles substantial admin work instead. For a per-diem hygienist, the dental offices she's assigned to aren't locations where she runs her own business — she doesn't manage her own billing, scheduling, or 1099 reconciliation from any of them, a dentist's practice runs its own. That means there usually is no other fixed location doing substantial admin work for her business, which clears the harder half of the test by default. What she still needs is a specific area of her home used regularly and exclusively for that administrative work — confirming assignments, reconciling multiple 1099s, maintaining her mileage log, ordering her own instruments — not just occasionally checking a staffing app from the couch. A hygienist who sets aside even a small dedicated desk or nook for this and genuinely limits it to business use clears both halves of the test. Once this qualifies, it isn't only a home-office deduction (a modest one, at $5 per square foot up to 300 square feet under the simplified method in Rev. Proc. 2013-13) — it's also what makes her home her 'principal place of business' for purposes of Publication 463's separate mileage exception, turning every drive to an assignment into deductible business mileage regardless of distance. Without that dedicated space, the plain commuting rule applies instead: see the mileage question above for what that means for her deduction.

Does a dental hygienist ever have Cost of Goods Sold?

Not in the ordinary per-diem or temp-agency model — a hygienist paid for chairside time at someone else's practice has a pure service business, and since the host office supplies the consumables used during the visit (see above), there's no inventory on either side of the transaction. The one place this can change is retail resale: a hygienist who buys electric toothbrushes, specialized whitening trays, or take-home fluoride kits at wholesale and sells them directly to patients as a retail add-on — rather than simply recommending a product the practice or a third party sells — is reselling inventory, and the wholesale cost of units actually sold becomes Cost of Goods Sold on Schedule C Part III, the same distinction covered in this corpus's general COGS-vs-supplies guide. For most per-diem hygienists this never comes up; it's worth checking only if retail sales are actually part of your practice.

Dental Hygienist Tax Deductions: 2026 Schedule C Guide for Independent & Per-Diem Contract Hygienists

Published: September 29, 2026 · Reading time: 10 min

TL;DR: A self-employed dental hygienist files Schedule C and pays self-employment tax on net profit like any other contractor. What's genuinely different here: most of the PPE and consumables other health-gig posts in this corpus treat as a deductible expense are usually not yours to deduct — the host dental office supplies chairside disposables the same way it does for its own staff, while your own costs are a hand-instrument kit and magnification loupes instead. Mileage is the standout mechanic, and it hinges on the home office: without a qualifying home office, a per-diem hygienist's home-to-office drives within her own metro area are ordinary nondeductible commuting under IRS Publication 463 — only the drive between two offices on a multi-office day counts. A qualifying home office changes that completely: it makes her residence her principal place of business for administrative purposes, which unlocks Publication 463's separate rule that home-to-worksite mileage is deductible regardless of distance — at the July 1 rate split ($0.725 to $0.76/mile). The home-office test itself is easier to clear than it looks, for a reason specific to this trade. On the QBI side, dental hygiene reads as a fairly clean health-field SSTB, a cleaner call than some other licensed trades get. And this is one of a small number of posts in this corpus that has to flag a worker-misclassification question honestly, because the line between a genuinely independent per-diem hygienist and an employee paid on a 1099 to dodge payroll taxes is a real one in this specific field. The worked example below runs a realistic solo year and checks all three §199A limits.

Most self-employed health-adjacent trades in this corpus buy their own gloves, masks, and disposables and drive to one client after another for one employer relationship. A per-diem dental hygienist's return inverts the first of those assumptions and complicates the second. The dental office she's assigned to for the day supplies almost everything she touches at chairside; what she owns herself is a personal instrument kit and a pair of loupes. And whether her drives to a rotating slate of offices are deductible business mileage or ordinary commuting turns on a home-office test most rotating-assignment posts skip past — a test this guide gets right by working from the regulation's actual text rather than a plausible-sounding shortcut. That inversion, plus a licensing question and a worker-classification question this specific field raises more sharply than most, is what makes this return worth its own guide.

Before Anything Else: Are You Actually Self-Employed Here?

This matters enough to address up front, because it changes whether anything below even applies. Most states' dental practice acts require hygienists to work under some form of dentist supervision, and a hygienist who works exclusively for one practice, on a schedule that practice sets, using instruments and protocols that practice controls, looks a great deal like a common-law employee regardless of whether that practice hands her a 1099 instead of a W-2 at year end. Paying 1099 income to someone who is functionally an employee doesn't make them a contractor — it shifts the employer's payroll-tax and benefits cost onto the worker, and it's the exact fact pattern Form 8919 and the broader 1099-vs-W-2 worker-classification test exist to address.

Genuine self-employment in this field looks different: a hygienist who takes assignments across multiple, unrelated dental offices through a staffing platform or her own outreach, sets her own rate or accepts a posted one, brings her own instruments, and isn't required to work exclusively for any one practice has a real claim to contractor status. This guide assumes that fact pattern. If a single office is your only client and it controls your schedule and methods, the deductions below may still be correct, but the more important question is whether you should be receiving a W-2 in the first place.

PPE, Your Own Instrument Kit, and Loupes — Line 22

Here's the inversion worth understanding before anything else on this return: the host dental office almost always supplies the chairside consumables — gloves, masks, prophy paste, saliva ejectors, disposable barriers — the same way it supplies them to its own employees, because running a compliant clinical operation is the practice's responsibility regardless of who's in the chair that day. Buying your own on top of that is unusual in this trade and isn't the norm the way it is for a caregiver or phlebotomist working outside any host facility's clinical infrastructure.

What a hygienist typically does buy and own herself:

A personal hand-instrument kit — scalers, curettes, mirrors, and periodontal probes set up to her own preference and technique, carried from office to office. This is a genuine professional norm in the field, not an eccentricity: instruments are tools of the trade the way a stylist owns her own shears.
Magnification loupes and an LED headlight — typically $1,000–$3,000, and usually $2,500 or less per item.

Both qualify for the de minimis safe harbor under Notice 2015-82, which set the regulatory ceiling at $2,500 per item for a taxpayer without an applicable financial statement — current-year Line 22 supplies, no depreciation schedule required. Personal protective equipment you do buy for yourself beyond what the host office supplies — a personal N95 for immunocompromised patients, your own loupe-light batteries — is deductible the same way.

Professional Liability Insurance — Line 15

Professional liability (malpractice) insurance for a hygienist covers a claim arising from a scaling injury, a missed periodontal finding, or an anesthesia-related complication in states where hygienists administer it. This is a straightforward Line 15 deduction. Your own personal health insurance is not part of this line — per the self-employed health insurance deduction, that's claimed separately on Schedule 1.

The Vehicle: Why This Return's Mileage Depends on the Home Office

This is the mechanic that makes a per-diem hygienist's return genuinely different from almost anything else in this corpus — but the popular version of it (rotating assignments automatically make every mile deductible) is wrong, and the correct version runs through the home-office test below, not around it.

The general rule for everyone is that driving from home to a regular workplace is a nondeductible commute. IRS Publication 463 states it directly: "Daily transportation expenses you incur while traveling from home to one or more regular places of business are generally nondeductible commuting expenses." Its "no regular place of business" exception is narrower than it sounds: "Unless you have a regular place of business, you can only deduct your transportation expenses to a temporary work location outside your metropolitan area." A hygienist rotating through several dental offices, all inside the metro area where she lives, doesn't clear that exception just by lacking one fixed office — it only helps for a genuinely out-of-town assignment.

Within her own metro area, other rules govern instead:

Second job: "If you regularly work at two or more places in one day, whether or not for the same employer, you can deduct your transportation expenses of getting from one workplace to another." On a day she works two offices, the drive between them is deductible — but the first drive of the day (home to the first office) and the last drive (an office back home) are still ordinary commuting.
A regular work location away from home: daily transportation expenses can also be deducted "if (1) you have one or more regular work locations away from your residence." A hygienist with one genuinely steady office — even alongside other rotating assignments — can deduct home-to-temporary-assignment mileage on this basis alone, without needing a qualifying home office at all. This doesn't help someone with no regular work location anywhere.
Residence as principal place of business: daily transportation expenses can also be deducted "if ... (2) your residence is your principal place of business and you incur expenses going between the residence and another work location in the same trade or business, regardless of whether the work is temporary or permanent and regardless of the distance."

That third rule is the one that actually turns nearly every mile deductible for a hygienist with no regular office anywhere — and whether it applies turns entirely on the home-office test in the next section, not on how many different offices she works at.

This is a facts-based test, not a permanent label. A hygienist who stops maintaining the dedicated administrative space the home-office test requires loses this treatment going forward — revisit it honestly each year rather than assuming an answer from an earlier year still holds. Commuting vs. business miles covers the general version of this distinction.

Two methods either way:

Standard mileage rate: 2026 has two rates because the IRS revised the rate mid-year. $0.725 per mile applies to expenses paid or incurred January 1 through June 30 (IR-2025-128), and $0.76 per mile applies to expenses paid or incurred on or after July 1, 2026 (IR-2026-29) — both confirmed directly from the IRS standard mileage rates page.
Actual expenses: fuel, insurance, repairs, tires, and depreciation × business-use percentage.

Because assignments are often confirmed on short notice through a staffing app, a contemporaneous mileage log matters here as much as anywhere in this corpus — reconstructing which office you drove to on which day, six months later, from memory is exactly the kind of record an audit doesn't accept.

The Home Office — the Test Is Easier to Clear Than It Looks, and It's the Key to the Mileage Deduction Above

§280A(c)(1)'s flush language extends "principal place of business" to a home used for "the administrative or management activities of any trade or business of the taxpayer if there is no other fixed location of such trade or business where the taxpayer conducts substantial administrative or management activities of such trade or business." Read that test in two separate halves, because it's easy to apply it to the wrong one: "substantial" describes the other fixed location's admin activity, not the home's own. The question isn't whether a hygienist's home admin work is substantial enough on its own — it's whether some other fixed place is doing substantial admin work for the business instead.

For a per-diem hygienist, the dental offices she's assigned to almost never are. She doesn't run her billing, scheduling, or 1099 reconciliation out of any of them — those offices manage their own operations, not hers. With no other fixed location doing that kind of work, the harder half of the test is usually satisfied by default. What's left is the more ordinary requirement: a specific area of her home used regularly and exclusively for that administrative work — confirming assignments, reconciling several 1099s, maintaining a mileage log, ordering her own instruments. A hygienist who sets aside even a small dedicated space for this, and keeps it to business use, clears both halves.

Once that's true, two things follow: a modest home-office deduction itself (this guide's worked example below doesn't claim it, to keep the focus on the mileage mechanic, but the simplified method allows $5 per square foot up to 300 square feet under Rev. Proc. 2013-13), and — more consequentially — her residence becomes her principal place of business for Publication 463's mileage exception, which is what makes the vehicle deduction above work at all. Without that dedicated space, neither applies: the plain commuting rule governs her drives, as the mileage section above describes.

This same administrative-activities route is also available to a hygienist running a genuinely independent public-health or mobile-hygiene practice — the kind that exists in roughly 43 "direct access" states, where a hygienist can treat patients without a dentist's prior exam, commonly serving schools, Head Start programs, and long-term-care facilities with portable equipment. The analysis is identical either way; a practice like that just tends to have an even clearer administrative footprint to point to.

Licensing and Continuing Education vs. Becoming Licensed in the First Place

Not deductible: the accredited dental hygiene degree program, the National Board Dental Hygiene Examination (NBDHE) fee, and a regional or state clinical licensing exam fee. Treas. Reg. §1.162-5(b)(3)(i) places "expenditures made by an individual for education which is part of a program of study being pursued by him which will lead to qualifying him in a new trade or business" in the nondeductible category — this applies even to someone who worked in an unrelated field before, because dental hygiene is its own credentialed trade with its own accredited coursework and licensing exams.

Deductible, on Line 27a: continuing-education hours required to renew an existing RDH license, the renewal fee itself, and professional association dues. The regulation's own Example 3 confirms the logic: a physician's two-week course "reviewing new developments in several specialized fields of medicine" is deductible because it "maintains or improves skills required by him in his trade or business and does not qualify him for a new trade or business." Same kind of activity — coursework, a fee — with opposite outcomes depending on whether you already hold the credential it maintains.

Advertising and Everything Else

Advertising (Line 8): a boosted profile on a hygiene staffing platform, a personal website, local practice outreach.
Contract labor (Line 11): if you ever pay a covering hygienist for an assignment you can't take. Track the running total per person — the information-reporting threshold for issuing that person a Form 1099-NEC is $2,000 for payments made after December 31, 2025, up from the old $600 figure, per OBBBA §70433.
Quarterly estimated taxes: income arriving as separate 1099-NEC payments from several offices or a staffing platform, on different schedules, is exactly the lumpy timing that distorts a quarter's estimate if it isn't planned for — reconcile each 1099 against your own hours log before you file, not after a mismatch notice arrives.

The QBI Deduction: Is Dental Hygiene a Health-Field SSTB?

26 U.S.C. §199A(d)(2)(A) pulls its list of specified fields from §1202(e)(3)(A): "health, law, engineering, architecture, accounting, actuarial science, performing arts, consulting, athletics, financial services, brokerage services, or any trade or business where the principal asset ... is the reputation or skill of 1 or more of its employees" (§199A disregards "engineering, architecture" from that list). Treas. Reg. §1.199A-5(b)(2)(ii) defines the health field: "the performance of services in the field of health means the provision of medical services by individuals such as physicians, pharmacists, nurses, dentists, veterinarians, physical therapists, psychologists, and other similar healthcare professionals performing services in their capacity as such." It separately excludes "the provision of services not directly related to a medical services field, even though the services provided may purportedly relate to the health of the service recipient" — naming health-club operation, payment processing, and pharmaceutical/device research and manufacturing as examples that don't count.

Dental hygienists aren't named in that list by title, but the work is squarely inside the pattern the regulation describes. A hygienist performs a prophylaxis, scales and root-plans periodontally involved teeth, charts periodontal pocket depths and makes a clinical assessment of a patient's gum health, exposes and interprets dental radiographs, applies sealants and fluoride, and — in most states — administers local anesthesia or nitrous oxide directly to a patient. That's real clinical judgment and direct patient care, not a technical procedure performed without judgment. The regulation's own Example 1 (§1.199A-5(b)(3)(i)) is instructive by comparison: a pharmacist "performing inoculations" — a needle procedure on a patient — is held to be "engaged in the performance of services in the field of health," and a hygienist's scope of practice, especially in a state where she administers anesthesia, involves comparable clinical contact. That's a meaningfully closer fit than Example 4's lab-technical staff, who have no patient contact at all and "do not diagnose, treat, or manage any aspect of patient care" — the fact pattern the regulation held outside the health field.

No IRS example addresses hygienists by name, so treat this as reasoned analysis rather than settled law, and confirm it in writing with an EA or CPA if your household income puts this within reach of the threshold below.

That conclusion matters only in combination with three independent checks:

SSTB phase-out — even treating dental hygiene as an SSTB, this only bites above the 2026 threshold: $201,750 single/head-of-household, $403,500 married filing jointly (Rev. Proc. 2025-32). The deduction phases to zero over the next $75,000 (single) or $150,000 (joint) of taxable income above that, per §199A(d)(3)(A). Most solo per-diem hygienists are well under this.
W-2 wage / 2.5%-of-property cap — also only engages above that same threshold; a solo practice with no employees and modest equipment clears it easily below that level regardless of SSTB status.
20%-of-taxable-income cap — applies to every filer at every income level, SSTB or not. §199A(a)(2) caps the deduction at the lesser of 20% of qualified business income or 20% of taxable income over net capital gain, and §199A(e)(1) computes that taxable income without regard to the QBI deduction itself, but after the standard or itemized deduction. This is very often the cap that actually binds in a solo year, independent of the SSTB question entirely.

A Realistic Solo Year

A single-filer dental hygienist working per-diem assignments across four to five dental offices through a hygiene staffing platform, no employees, standard deduction, 2026. She keeps a small dedicated desk at home — used regularly and exclusively to confirm assignments, reconcile 1099s from multiple offices, and log mileage — and no other fixed location handles that administrative work for her, so her home qualifies as her principal place of business for that purpose and every assignment mile is deductible regardless of distance:

node -e "
const hoursTotal = 970; // per-diem/temp hours across 4-5 dental offices via a hygiene staffing platform, blended across the year
const blendedRate = 68; // blended hourly rate across offices/platform assignments
const grossReceipts = hoursTotal * blendedRate;

const instrumentKit = 640; // personal hand-instrument kit (scalers, curettes, mirrors, probes) carried office to office -- <= \$2,500, de minimis safe harbor
const loupesHeadlight = 1450; // magnification loupes + LED headlight, <= \$2,500, de minimis safe harbor
const suppliesLine22 = instrumentKit + loupesHeadlight; // host offices supply chairside disposables -- NOT her expense

const liabilityInsuranceLine15 = 140; // professional liability insurance
const ceRenewal = 385; // CE hours + license renewal fee to maintain the EXISTING RDH license
const membershipDues = 120; // ADHA / state hygiene association dues
const otherLine27a = ceRenewal + membershipDues;

const advertisingLine8 = 90; // staffing-platform profile boost / local listing

const milesH1 = 4300, rateH1 = 0.725; // home qualifies as principal place of business for admin activities (Sec 280A(c)(1) flush language) -- no other fixed location handles the business's admin work, so home-to-assignment mileage is deductible under Pub. 463's residence exception, regardless of distance
const milesH2 = 4600, rateH2 = 0.76;
const vehicleLine9 = milesH1 * rateH1 + milesH2 * rateH2;

const partIIExpenses = suppliesLine22 + liabilityInsuranceLine15 + otherLine27a + advertisingLine8 + vehicleLine9;

const netProfit = grossReceipts - partIIExpenses; // simplified home-office deduction ($5/sq ft, Rev. Proc. 2013-13) is available but not claimed here, to isolate the mileage mechanic

const initialLicenseCost = 5200; // NOT deductible -- hygiene program tuition + NBDHE + regional clinical board exam, new trade, excluded from partIIExpenses

const seTaxable = netProfit * 0.9235;
const ssWageBase2026 = 184500;
const oasdiTaxable = Math.min(seTaxable, ssWageBase2026);
const oasdi = oasdiTaxable * 0.124;
const medicare = seTaxable * 0.029;
const seTax = oasdi + medicare;
const halfSeTaxDeduction = seTax / 2;

const standardDeduction = 16100; // 2026 single, Rev. Proc. 2025-32
const qbi = netProfit - halfSeTaxDeduction;
const taxableIncomeBeforeQBI = netProfit - halfSeTaxDeduction - standardDeduction; // Sec 199A(e)(1): WITHOUT the QBI deduction itself

const tentativeQbiDeduction = qbi * 0.20;
const taxableIncomeCap = taxableIncomeBeforeQBI * 0.20;
const qbiDeduction = Math.min(tentativeQbiDeduction, taxableIncomeCap);

const finalTaxableIncome = taxableIncomeBeforeQBI - qbiDeduction;

const fmt = n => n.toLocaleString('en-US', {minimumFractionDigits:2, maximumFractionDigits:2});

console.log('grossReceipts (Line 1)', fmt(grossReceipts));
console.log('suppliesLine22 (Line 22)', fmt(suppliesLine22));
console.log('liabilityInsuranceLine15 (Line 15)', fmt(liabilityInsuranceLine15));
console.log('otherLine27a (Line 27a)', fmt(otherLine27a));
console.log('advertisingLine8 (Line 8)', fmt(advertisingLine8));
console.log('vehicleLine9 (Line 9)', fmt(vehicleLine9));
console.log('partIIExpenses (Line 28)', fmt(partIIExpenses));
console.log('netProfit (Line 31)', fmt(netProfit));
console.log('initialLicenseCost (NOT deductible, excluded)', fmt(initialLicenseCost));
console.log('seTaxable (92.35%)', fmt(seTaxable));
console.log('seTax total', fmt(seTax));
console.log('halfSeTaxDeduction', fmt(halfSeTaxDeduction));
console.log('QBI', fmt(qbi));
console.log('taxableIncomeBeforeQBI', fmt(taxableIncomeBeforeQBI));
console.log('tentativeQbiDeduction (20% of QBI)', fmt(tentativeQbiDeduction));
console.log('taxableIncomeCap (20% of TI before QBI)', fmt(taxableIncomeCap));
console.log('qbiDeductionAllowed', fmt(qbiDeduction));
console.log('finalTaxableIncome', fmt(finalTaxableIncome));
"

Output:

grossReceipts (Line 1) 65,960.00
suppliesLine22 (Line 22) 2,090.00
liabilityInsuranceLine15 (Line 15) 140.00
otherLine27a (Line 27a) 505.00
advertisingLine8 (Line 8) 90.00
vehicleLine9 (Line 9) 6,613.50
partIIExpenses (Line 28) 9,438.50
netProfit (Line 31) 56,521.50
initialLicenseCost (NOT deductible, excluded) 5,200.00
seTaxable (92.35%) 52,197.61
seTax total 7,986.23
halfSeTaxDeduction 3,993.12
QBI 52,528.38
taxableIncomeBeforeQBI 36,428.38
tentativeQbiDeduction (20% of QBI) 10,505.68
taxableIncomeCap (20% of TI before QBI) 7,285.68
qbiDeductionAllowed 7,285.68
finalTaxableIncome 29,142.71

Item	Schedule C line	Amount
Per-diem hygiene assignments (970 hours, blended $68/hr)	1	$65,960.00
Gross receipts	1	$65,960.00
Supplies — own instrument kit + loupes/headlight	22	$2,090.00
Professional liability insurance	15	$140.00
Other expenses — CE/renewal $385 + dues $120	27a	$505.00
Advertising	8	$90.00
Vehicle — 8,900 mi split at $0.725 / $0.76, home qualifies as principal place of business	9	$6,613.50
Total Part II expenses	28	$9,438.50
Net profit	31	$56,521.50

Gross receipts of $65,960.00 come entirely from per-diem hourly assignments — there's no Cost of Goods Sold anywhere in this return, because the host offices supply the consumables used at chairside and this hygienist doesn't sell retail products. Part II expenses total just $9,438.50 against that revenue, dominated by $6,613.50 in vehicle costs — every mile of which is deductible because her home qualifies as her principal place of business for administrative purposes: no dental office she's assigned to handles her own billing or scheduling, so no other fixed location clears the "substantial administrative activities" bar, and her small dedicated home desk satisfies the regular-and-exclusive-use half of the test. This example doesn't separately claim the modest home-office deduction ($5/sq ft under Rev. Proc. 2013-13) that same qualifying space would also allow, to keep the focus on the mileage mechanic it unlocks. Not included anywhere in that $9,438.50: the $5,200.00 this hygienist spent, in a prior year, on her hygiene program tuition, NBDHE fee, and regional clinical board exam. That cost was real and paid in cash, and it still isn't deductible in any year — it qualified her for the trade she's now running, not for continuing to run it.

On the QBI side: half the self-employment tax deduction ($3,993.12) brings qualified business income to $52,528.38. Subtracting the $16,100.00 standard deduction puts taxable income before the QBI deduction at $36,428.38 — far under the $201,750 single SSTB threshold, so neither the phase-out nor the W-2-wage/property cap engages regardless of how firmly the SSTB analysis above holds. A naive "20% of QBI" calculation would claim $10,505.68. But the 20%-of-taxable-income cap is only $7,285.68 — short of the naive figure by exactly $3,220.00 (20% of the $16,100.00 standard deduction, the gap that recurs for any single filer with no other income taking the standard deduction), independent of the SSTB question entirely. The allowed QBI deduction is $7,285.68. Final taxable income: $29,142.71, which falls inside the 2026 single 12% bracket ($12,400–$50,400, per Rev. Proc. 2025-32, Table 3).

Audit Triggers & Common Mistakes

Deducting gloves, masks, and prophy paste the host office already supplied. Unlike most other health-gig trades in this corpus, these usually aren't your expense — check what the office provides before claiming consumables that were never actually your purchase.
Claiming home-to-office mileage as business miles just because assignments rotate, without a qualifying home office or a regular work location behind it. A rotating schedule alone doesn't make home-to-work drives deductible inside your own metro area — that requires either a home that genuinely qualifies as your principal place of business for administrative purposes, or a genuinely regular work location elsewhere. Without either, only the drive between two offices on a multi-office day is deductible.
Deducting the hygiene-program tuition or NBDHE/clinical-board exam fees as a current-year business expense. Treas. Reg. §1.162-5(b)(3) treats this as a nondeductible personal capital expense regardless of when it was paid or what field you worked in before.
Assuming the home-office test requires a large administrative operation. It doesn't — "substantial" in §280A(c)(1)'s flush language describes some other fixed location's admin activity, not the size of the home admin work itself. A small dedicated space, used regularly and exclusively, clears it when (as is typical here) no other fixed location handles the business's admin work.
Treating a single-practice, hours-and-methods-controlled 1099 arrangement as automatically self-employed. If one office is your only client and it functions like an employer in every way except the tax form it files, the deductions in this guide may be correct but the classification underneath them may not be — see the worker-classification guides linked above.
Skipping the July 1 mileage-rate split. A full year of business miles at a single annual rate understates the deduction for every mile driven after the increase.
Claiming a flat "20% of profit" for QBI without checking the taxable-income cap. The SSTB analysis above is real, but the ordinary 20%-of-taxable-income cap — which applies to every filer regardless of SSTB status — is what actually binds in most solo-practice years.

The defense in every case is the same: tag the category at the moment of the transaction — an office-supplied consumable versus your own instrument purchase, a home-office-qualifying drive versus an ordinary commute, license renewal versus original licensing cost — rather than reconstructing a year of scattered 1099-NEC deposits from several offices in April, and keep records for the period the IRS expects.

How CentSense Helps

CentSense tags every instrument purchase, insurance premium, and assignment mile to the right Schedule C line the moment you capture it:

Scan your instrument-kit, loupes, and liability-insurance receipts with AI, tagged to Line 22 and Line 15 respectively instead of a generic "supplies" bucket
Log home-to-assignment miles automatically, with the two 2026 half-year rates applied to the correct halves of the log
Flag CE and license-renewal receipts as Line 27a, and separate anything that looks like an original-licensing cost before it's deducted incorrectly
Track each office or platform's 1099-NEC against your own hours log throughout the year, not just at tax time
Export a CPA-ready category breakdown as CSV when the return is due

Authoritative References

Stop guessing whether last Tuesday's drive to a fill-in assignment was deductible mileage or a nondeductible commute, or which office's 1099 that deposit belongs to. Start a free CentSense account, scan every instrument, insurance, and CE receipt with AI the day it arrives, log home-to-assignment miles at the correct half-year rate, and export a CPA-ready Schedule C breakdown at tax time. The free tier includes 10 AI receipt scans a month, no credit card required, and the Solo plan is $5/month for unlimited scans, mileage tracking, and a CPA-ready CSV export. Start free →

This guide is general education for U.S. self-employed dental hygienists filing a Schedule C in 2026. It is not personalized tax advice, and it is not a substitute for state-specific dental-practice-act guidance, a worker-classification determination, or a written opinion on your own SSTB or home-office facts, which a CPA or EA should confirm based on your full situation.

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