Switching From Standard Mileage to Actual Expenses: How to Compute Depreciation Under Rev. Proc. 2019-46

Published: September 22, 2026 · Reading time: 12 min

TL;DR: Nearly every vehicle-deduction guide mentions, in one sentence, that you can switch from the standard mileage rate to actual expenses in a later year. Almost none show what that switch actually computes. Rev. Proc. 2019-46 §4.05(3) requires straight-line depreciation over the car's remaining estimated useful life — a different, undefined concept from the ordinary MACRS recovery period — starting from a basis your standard-mileage years have already reduced through the rate's built-in depreciation component, and still subject to the §280F luxury-auto dollar caps even though you never claimed a dollar of MACRS before. In the worked example below, a $34,000 vehicle enters its switch year with a $22,987 adjusted basis, computes to $11,493.50/year of straight-line depreciation over a 2-year remaining life — and the §280F cap knocks that down to $7,160/year, stretching full recovery of the basis out to four actual tax years instead of two.

Every comparison of the standard mileage rate against the actual expense method — including several on this site — states the lock-in rule the same way: choose standard mileage in year one, and you keep the option to switch to actual expenses later; choose actual expenses (especially with Section 179 or bonus depreciation) in year one, and you're locked into actual expenses for that car for good. That much is accurate as far as it goes. What none of them walk through is the other side of the sentence — what "switch to actual expenses later" actually requires you to compute once you do it. That's a real gap: the switch has its own basis rule, its own depreciation method, and its own interaction with the luxury-auto caps, none of which are the same as an ordinary Form 4562 depreciation schedule for a car you depreciated with MACRS from day one.

The One-Way Door, and What It Locks

Using the standard mileage rate isn't just a simpler deduction method — it's an election. Rev. Proc. 2019-46, which governs the standard mileage rate, states it plainly in Section 4.05(3):

"By using the business standard mileage rate, the taxpayer has elected to exclude the automobile, if owned, from MACRS pursuant to §168(f)(1)."

That's not a figure of speech. IRC §168(f)(1) excludes from MACRS any property a taxpayer elects to depreciate under "a method of depreciation not expressed in a term of years" — and a flat cents-per-mile rate is exactly that. Every year you take the standard mileage rate, you're affirmatively opting the vehicle out of the ordinary depreciation system, not simply choosing a shortcut within it.

The same section spells out what locks you out of ever using standard mileage on that car again:

"A taxpayer may not use the business standard mileage rate to compute the deductible expenses of an automobile for which the taxpayer has (a) claimed depreciation using a method other than straight-line for its estimated useful life, (b) claimed a §179 deduction, (c) claimed the additional first-year depreciation allowance under, for example, §168(k) ..., or (d) used the Accelerated Cost Recovery System (ACRS) ... or the Modified Accelerated Cost Recovery System (MACRS)."

Most guides shorthand this as a "first-year election," and in practice that's usually when it happens — you decide how to depreciate a new vehicle the first year it's in service, and that decision typically sticks. But read closely, the rule isn't actually keyed to year one. It's keyed to whether you've ever claimed one of those four things on this specific vehicle. A car can spend three years on standard mileage and still be switched to actual expenses in year four — that's the scenario this guide walks through — but the moment you claim accelerated depreciation, §179, or bonus depreciation after the switch, the door back to standard mileage closes permanently for that car.

The next sentence in §4.05(3) is the part almost nothing in the corpus works through:

"If, after using the business standard mileage rate, the taxpayer uses actual costs, the taxpayer must use straight-line depreciation for the automobile's remaining estimated useful life, subject to the applicable depreciation deduction limitations under §280F."

Three separate constraints are packed into that one sentence — a required method, an undefined time period, and a dollar ceiling that wasn't supposed to matter to a standard-mileage filer. Each one is worth unpacking with real numbers.

Step One: The Basis You're Actually Switching With

You don't start the switch year depreciating your original purchase price. The corpus already covers, in full, how the standard mileage rate's built-in depreciation component reduces basis for an ordinary sale — the mechanics carry over unchanged here. Every business mile you deducted with the standard rate, in every year you used it, was deemed depreciation equal to that year's IRS-published depreciation component (a distinct figure from the mileage deduction rate itself, confirmed directly from IRS Notice 2026-10, Section 4):

Meet Naomi

Naomi Castellanos is a freelance home inspector. She bought a $34,000 dedicated inspection vehicle — a compact SUV, rated well under 6,000 lbs GVWR, so it's squarely a "passenger automobile" for §280F purposes — and placed it in service on March 1, 2024. It's a 100%-business vehicle; she drives her own car for everything personal. She used the standard mileage rate for 2024, 2025, and 2026:

That 2026 row deserves a note, because 2026 is the year the mileage rate itself split mid-year. The 2026 business mileage deduction rate changed to $0.725 per mile from January 1 through June 30, and $0.76 per mile from July 1 through December 31, under Notice 2026-10 as modified by Announcement 2026-11. Naomi's actual 2026 mileage deduction reflects that split — 5,300 miles at $0.725 plus 6,700 miles at $0.76, for $8,934.50 claimed on Schedule C Line 9. But the depreciation component that reduces her basis is a different number from a different section of the same notice, and it did not split: Announcement 2026-11 revised only "the optional standard mileage rates for computing the deductible costs of operating an automobile," and its own text confirms "all other provisions of Notice 2026-10 remain in effect" — including Section 4's depreciation-component figure. So all 12,000 of Naomi's 2026 business miles reduce her basis at the same flat 35 cents, regardless of whether the mile was driven in March or November.

node -e '
const cost = 34000;
const reduction2024 = 9400 * 0.30;
const reduction2025 = 12100 * 0.33;
const reduction2026 = 12000 * 0.35;
const total = reduction2024 + reduction2025 + reduction2026;
console.log(reduction2024, reduction2025, reduction2026, total, cost - total);
'

2820 3993 4200 11013 22987

Naomi's adjusted basis entering the switch year is $34,000.00 − $11,013.00 = $22,987.00. That's the number the rest of this computation runs on — not $34,000.

Step Two: Straight-Line Over an Undefined "Remaining Estimated Useful Life"

Here's the gap in the Rev. Proc. itself: it tells you the method (straight-line) but never states a number for the "remaining estimated useful life." That phrase is deliberate, not sloppy — a taxpayer who used standard mileage was excluded from MACRS under §168(f)(1) from day one, so there's no MACRS "recovery period" running in the background to fall back on. Several posts already on this site shorthand the post-switch depreciation as running over "the remaining recovery period" — that's an understandable practitioner simplification, but it's not the phrase the revenue procedure actually uses, and the two concepts aren't guaranteed to be identical.

What is defined is the automobile's property class. IRS Publication 946 lists "Automobiles, taxis, buses, helicopters, and trucks" under 5-year property — the only period the tax code specifies for this asset class at all. In the absence of a different number from the IRS for this specific switch, that 5-year figure is the working estimate of useful life most preparers use. Naomi placed her vehicle in service in 2024; by the start of 2027, three years (2024, 2025, 2026) of that estimated 5-year life have elapsed, leaving an estimated 2 years remaining (2027 and 2028).

node -e '
const adjBasis = 22987;
const remainingYears = 2;
console.log(adjBasis / remainingYears);
'

11493.5

Straight-line over that 2-year remaining life comes to $11,493.50 per year for 2027 and 2028 — before the next constraint applies.

Step Three: The §280F Cap Applies Anyway

This is the part that surprises freelancers who assume the luxury-auto caps are an actual-expense-method problem they simply never had, since they'd been on standard mileage all along. They're wrong to assume that. §4.05(3)'s straight-line requirement is explicitly "subject to the applicable depreciation deduction limitations under §280F," and those limitations attach to the vehicle from the calendar year it was placed in service — 2024 for Naomi — and apply, per Rev. Proc. 2024-13's own scope section, "for each taxable year that the passenger automobile remains in service." That includes every year Naomi was on standard mileage, even though no separate depreciation figure mattered to her during those years; it also means the switch year in 2027 uses the dollar limits from the 2024 placed-in-service table, not a table for 2027.

Naomi never claimed the §168(k) bonus depreciation allowance (she was never inside MACRS to claim it), so Rev. Proc. 2024-13's Table 2 — depreciation limitations for automobiles placed in service in 2024 with no §168(k) bonus depreciation — is the one that applies to her:

2027 is Naomi's fourth tax year of ownership (2024 = 1st, 2025 = 2nd, 2026 = 3rd, 2027 = 4th) — so the $7,160 "each succeeding year" cap applies, and it keeps applying every year after, including 2028. Her uncapped straight-line figure of $11,493.50 is well above that ceiling, so the cap binds in both years:

node -e '
const straightLine = 11493.5;
const cap = 7160;
const ded2027 = Math.min(straightLine, cap);
const ded2028 = Math.min(straightLine, cap);
console.log(ded2027, ded2028, ded2027 + ded2028);
'

7160 7160 14320

Naomi deducts $7,160.00 in 2027 and $7,160.00 in 2028 — $14,320.00 total — against a $22,987.00 basis. That leaves $8,667.00 of basis un-recovered when her nominal 2-year "remaining estimated useful life" runs out at the end of 2028.

Step Four: The Cap Outlives the Nominal Life — the §280F(a)(1)(B) Carryforward

That $8,667.00 doesn't vanish, and it isn't lost. §280F(a)(1)(B) — confirmed directly from the statute — provides that "unrecovered basis... shall be treated as an expense for the 1st taxable year after the recovery period," and any excess still remaining "shall be treated as an expense in the succeeding taxable year." In plain terms: once the nominal life is over, you keep deducting the leftover basis, still capped at the same "each succeeding year" dollar amount, for as many additional years as it takes to fully recover it.

node -e '
let remaining = 22987 - 14320;
const cap = 7160;
const ded2029 = Math.min(remaining, cap);
remaining -= ded2029;
const ded2030 = Math.min(remaining, cap);
remaining -= ded2030;
console.log("unrecovered after 2028:", 22987 - 14320);
console.log("2029:", ded2029, "remaining:", remaining + ded2030);
console.log("2030:", ded2030, "remaining after:", remaining);
'

unrecovered after 2028: 8667
2029: 7160 remaining: 1507
2030: 1507 remaining after: 0

Naomi's $22,987.00 adjusted basis is fully depreciated across four actual tax years — 2027 through 2030 — even though the nominal "remaining estimated useful life" the switch was computed against was only two years. That's the §280F cap doing exactly what it does for any capped vehicle: stretching real-world recovery past the period the depreciation method nominally covers. It's the same mechanic that already shows up when a car is totaled or traded in mid-recovery — here it's triggered by a method switch instead of a disposition.

The Records the Switch Actually Requires

This computation is only defensible with records most freelancers don't think to keep once they're comfortably filing a simple per-mile deduction:

• Every year's business-mile total for every year the standard mileage rate was used on this vehicle — the input to the basis-reduction calculation, and something a contemporaneous mileage log already gives you.
• The original purchase price and placed-in-service date, which fixes both the starting basis and which year's §280F table governs the car for its entire life.
• A written confirmation that no accelerated depreciation, §179, or bonus depreciation was ever claimed on this vehicle — the fact that makes the switch to actual expenses legal in the first place under §4.05(3).
• A depreciation worksheet for the switch year itself, run before you file, since Form 4562 has no line that walks a preparer through "remaining estimated useful life starting from a standard-mileage-reduced basis" — that computation has to be done outside the form and the result entered on it.
• The applicable §280F table for the vehicle's original placed-in-service year, kept with the vehicle's file for as long as you own it — you'll need the same table again in every succeeding year, including any carryforward years after the nominal life ends.

Common Mistakes

1. Depreciating from the original purchase price instead of the standard-mileage-reduced basis. The years on standard mileage already took deemed depreciation; skipping that step overstates every year of post-switch depreciation.
2. Confusing the depreciation component with the mileage deduction rate. The 2026 mileage deduction rate split to $0.725/$0.76 at July 1; the depreciation component that reduces basis stayed a flat 35¢ all year. Using the split figure to compute basis reduction is the wrong number from the wrong section of the notice.
3. Assuming "remaining recovery period" and "remaining estimated useful life" are interchangeable. The revenue procedure uses the second phrase deliberately, because a standard-mileage vehicle was never inside MACRS's defined recovery periods to begin with. Treat the 5-year figure as a working convention, not guidance the IRS states in so many words.
4. Assuming the §280F caps don't apply because no MACRS was ever claimed. They apply anyway, and they apply using the table for the year the car was originally placed in service — not the switch year.
5. Forgetting the carryforward after the nominal life ends. If the dollar cap kept the straight-line figure from fully depreciating the basis, the leftover amount is still deductible — capped the same way — in the years after the nominal period runs out, under §280F(a)(1)(B).
6. Not confirming eligibility before claiming actual expenses. If any earlier year on this vehicle involved accelerated depreciation, §179, or bonus depreciation, the switch described here was never available, and the vehicle should have stayed on actual expenses the whole time.
7. Trying to switch back to standard mileage after using an accelerated method post-switch. Once a car has any year of non-straight-line depreciation, §179, or bonus depreciation on it, Rev. Proc. 2019-46 §4.05(3) forecloses standard mileage on that vehicle permanently — there's no third switch back.

How CentSense Helps

The entire computation above depends on records from years most freelancers weren't thinking about a future depreciation switch when they logged them:

• Every year's business miles, saved and totaled automatically, so the basis-reduction calculation in Step One doesn't require reconstructing a mileage history from memory
• A per-vehicle deduction history that separates standard-mileage years from actual-expense years, so a switch-year computation starts from the right adjusted basis
• Route mileage logged automatically, split at the July 1 rate change for 2026 filers — the number that matters for the deduction itself, kept distinct from the depreciation component that doesn't split
• A record you can hand a CPA the moment a switch like this one is on the table, instead of assembling it after the fact

For the mechanics this guide builds on, see the depreciation component of the standard mileage rate and the §280F luxury-auto limits.

Authoritative References

• Rev. Proc. 2019-46, 2019-49 I.R.B. 1301 (rules for the optional standard mileage rates)
• 26 U.S.C. §168(f)(1) — Property to which MACRS does not apply (Cornell Law School Legal Information Institute)
• 26 U.S.C. §280F — Limitation on depreciation for luxury automobiles (Cornell Law School Legal Information Institute)
• 26 U.S.C. §1016 — Adjustments to basis (Cornell Law School Legal Information Institute)
• IRS Notice 2026-10 — 2026 Standard Mileage Rates (business rate and depreciation component)
• Internal Revenue Bulletin 2026-29 — Announcement 2026-11 (mid-year mileage rate revision, effective July 1, 2026)
• Rev. Proc. 2024-13 — Depreciation limitations for passenger automobiles placed in service during 2024
• IRS Publication 946 — How To Depreciate Property (5-year property classification for automobiles)

Don't reconstruct three years of mileage history the day you decide to switch methods. Start a free CentSense account and keep a per-vehicle deduction history — business miles, depreciation component, and method — ready before a switch like Naomi's ever comes up. Free tier includes 10 AI scans per month.

This guide is general education for U.S. self-employed freelancers filing a Schedule C in 2026. It is not personalized tax advice — eligibility to switch depreciation methods, the estimated useful life used for a specific vehicle, and the applicable §280F table all depend on your own facts and should be confirmed with a CPA or EA before filing. Figures reference IRS guidance dated for the years cited; a Schedule C filer with a different placed-in-service year should confirm the corresponding table for that year.