The IRS Says Your Subcontractor's Name and TIN Don't Match

Published: August 10, 2026 · Reading time: 12 min

TL;DR: You did the thing every guide tells you to do — collected the W-9 before you paid, filed the 1099-NEC by January 31. Then a CP2100A arrives saying the name and number don't match, and three clocks start together. 15 business days to mail the payee a B notice. No later than 30 business days before 24% backup withholding becomes mandatory on everything you pay them. 30 calendar days to stop once a certified W-9 comes back. The first B notice encloses a W-9; the second must not — the payee has to get validation from SSA or an IRS Letter 147C. It is reported on Form 945, never Form 941, due January 31, and Form 945 needs an EIN that matches the 1099s, which a sole proprietor filing under an SSN does not have. And the reason none of this is optional: if you don't withhold, you may become liable for the amount you failed to withhold — someone else's tax, out of your pocket, plus a §6721 and §6722 penalty charged twice for the same wrong number.

The corpus already tells you to get a W-9 before the first payment and to answer Lines I and J honestly. Both are about doing the paperwork correctly.

This is the case nobody plans for: you did the paperwork correctly and the paperwork was wrong anyway. The contractor transposed two digits. They gave you a business name but a personal SSN. They married and changed their surname with the Social Security Administration but not on the W-9 they sent you three years ago.

None of those are your fault, and all of them are now your problem.

Who this actually reaches

Any Schedule C filer who pays another person for services and files an information return about it. That is a bigger group than people expect:

If everyone you pay is paid by card or platform, this rule will never touch you — the same double-reporting carve-out that removes your 1099-NEC obligation moves the backup-withholding obligation to the processor too.

If you pay subcontractors by bank transfer or check, it can.

The notice is not a bill

A CP2100 or CP2100A notice tells you that a payee's name and TIN combination on a return you filed does not match IRS records, or that the TIN was missing. CP2100A goes to filers with fewer mismatches, CP2100 to larger ones. The obligations are identical.

What it is not:

• It is not a penalty notice. The proposed-penalty notice is a separate letter, Notice 972CG
• It is not an audit of your return
• It is not something the IRS will chase you about before the consequences attach

What it is: the trigger for three deadlines, each measured differently, which is the part that catches people out.

The three clocks

Two of them are business days and one is calendar days. Mixing that up in the wrong direction is expensive.

Work an actual date through it. A notice dated Tuesday, March 3, 2026:

• B notice due: 15 business days later → Tuesday, March 24, 2026
• Withholding mandatory from: 30 business days later → Tuesday, April 14, 2026

You may begin withholding earlier than April 14 — the rule is a deadline, not a start date. Many payers start immediately, because the alternative is tracking a second date six weeks out.

What 24% actually looks like

Priya subcontracts design work to Dev at $2,500 a month. The CP2100A arrives March 3. Dev doesn't respond to the B notice.

Dev has not lost the $600. It is an advance payment of Dev's own income tax and it shows up as withholding credit on Dev's return, exactly like an employee's paycheck withholding. But Dev will experience it as a short-paid invoice and will say so.

Now the version where Priya decides that is too awkward a conversation and pays in full anyway. Nine more monthly payments to year end:

• Payments made without withholding: $22,500
• Amount she should have withheld: $5,400
• The General Instructions: a payer who does not collect and pay over backup withholding as required may become liable for any uncollected amount

That is $5,400 of somebody else's tax, assessable against Priya, for the sake of avoiding one uncomfortable email. On top of it sit the information-return penalties below.

The two B notices are different documents

This is the single most-missed mechanic in the whole procedure.

First B Notice — sent when this is the first CP2100 or CP2100A you have received for that account:

• Encloses a Form W-9
• Asks the payee to complete and return it, certified
• Outer envelope marked conspicuously, e.g. IMPORTANT TAX INFORMATION ENCLOSED

Second B Notice — sent when it is the second within three calendar years:

• Does not enclose a Form W-9
• Tells the payee to get validation from the issuing agency instead: a Social Security card from SSA for an individual, or IRS Letter 147C for an EIN
• Same envelope marking

The logic is straightforward once stated: a second W-9 from the same person is just the same number the IRS has already rejected, written out again. The second notice forces the payee to go to the source.

Three refinements worth knowing:

• You generally do not have to send more than two B notices to the same account within three calendar years
• If a second CP2100 or CP2100A arrives in the same calendar year as the first, you may disregard it — no second B notice is required, even if it relates to a different tax year
• If a B notice comes back undeliverable, you must begin backup withholding. Try to find a better address, and keep the returned envelope with your records so you can prove where you are in the two-in-three-years count

Publication 1281 is blunt about whose job the tracking is: the backup-withholding regulations require payers to track the status of the notices they receive. There is no IRS-side counter you can query.

The "applied for a TIN" grace period does not help you

There is a rule that lets a payee write "Applied For" in the TIN block of a Form W-9 and buy 60 days before withholding starts.

It does not apply to nonemployee compensation. The General Instructions restrict that 60-day exemption to interest and dividend payments and certain payments on readily tradable instruments. Everything else — including the money you pay a subcontractor — is subject to backup withholding even while the payee is genuinely waiting on a TIN.

If a new contractor tells you their ITIN application is in process, the correct answer is that you will withhold 24% until the number arrives, and refund nothing afterwards — they claim the credit on their return.

Form 945, and the EIN problem underneath it

Backup withholding is nonpayroll withholding. It has its own annual return.

The two must be kept apart even for deposit arithmetic. You do not combine Form 945 amounts with Form 941 amounts when deciding whether the $2,500 threshold applies, whether you are a monthly or semiweekly depositor, or whether the $100,000 next-day rule bites. Under $2,500 for the year, you may simply pay with the return.

Then the detail that stops a lot of sole proprietors cold. Form 945 requires an EIN. The instructions say not to use an SSN or ITIN on a form that asks for an EIN, and that the name and EIN on Form 945 must match the name and EIN on the information returns reporting the withholding.

A freelancer who has always filed 1099-NECs under a Social Security number therefore needs to apply for an EIN — and the 1099s carrying the withholding have to be filed under that same EIN, so the switch has to happen before the January 31 filing, not after.

One more consequence: if you withheld, you must file the Form 1099 even if the payment was under the usual reporting threshold. The General Instructions require reporting backup withholding and the payment amount on the 1099 "even if the amount of the payment is less than the amount for which an information return is normally required." Withholding creates the filing obligation on its own.

The penalty is charged twice for one wrong number

Both. For the same mismatched TIN. So a single uncorrected wrong number on a single 1099-NEC is $680, and intentional disregard is at least $680 per return with no maximum.

Small-business annual caps — for average annual gross receipts of $5 million or less over the three most recent tax years — run $239,000, $683,000 and $1,366,000 at the three tiers. Comfortably above anything a solo operator will reach, which is the point: the caps are not the protection. The per-return amount is what you pay.

There is no de minimis escape for this error. The General Instructions list the things that are never inconsequential: a TIN, a payee's surname, and any money amount. A wrong TIN cannot be argued down as a harmless typo, because it is the specific class of error the exception excludes.

Two things do help, and both are worth knowing before you need them:

• Sending the B notice satisfies the annual solicitation requirement. Publication 1281 states it directly: sending a B notice in response to a CP2100 or CP2100A satisfies the solicitation you need in order to avoid the penalty for filing a return with an incorrect TIN. The response is the defence
• Reasonable cause survives, on the ordinary terms — an event beyond your control, significant mitigating factors, and evidence you acted responsibly both before and after the failure

The fix that costs nothing: match the TIN before you file

The IRS runs a free TIN Matching service through e-Services. You submit name and TIN combinations and it tells you whether they match before the information return goes anywhere. Payers of 1099-B, DIV, INT, K, MISC, NEC, OID, G and PATR income are eligible; you register once and must be listed on the Payer Account File.

The IRS's own expectation, in the General Instructions: payers who validate combinations before filing "will receive fewer backup withholding (CP2100) notices and penalty notices."

Ten minutes in January, against a process that otherwise costs you six weeks of deadlines, an awkward conversation with a contractor, a new EIN, an extra annual return, and up to $680 a head.

The record habit that makes this survivable

• Get the W-9 before the first payment, not at year end. A contractor you have already paid in full has no reason to answer your email in January
• Run TIN Matching on every new payee, and re-run anyone whose name has changed
• Keep the W-9 for at least four years after the due date of the return the payments relate to, alongside your other business records
• Log every CP2100 or CP2100A you receive, by payee and by calendar year. The two-in-three-years count is yours to maintain, and it is the only thing that tells you which B notice to send next time
• File the returned envelope when a B notice bounces. It is the evidence that you sent it

That fourth habit is the one people skip. The B notice you send this year determines the notice you must send in two years, and by then the original letter is in a drawer somewhere, if it exists at all.

Frequently Asked Questions

What is a CP2100 or CP2100A notice and what do I have to do about it?

It is the IRS telling you that a name and taxpayer identification number combination on an information return you filed does not match its records, or that a TIN was missing entirely. CP2100A goes to smaller filers and CP2100 to larger ones; the obligations are identical. It is not a bill and it is not a penalty notice, but it starts three separate clocks. You have 15 business days from the notice date, or from the date you received it if that is later, to send the payee a B notice asking them to fix the problem. You must begin backup withholding at 24% on reportable payments to that payee no later than 30 business days after you receive the notice. And you must stop withholding within 30 calendar days after the payee gives you a certified Form W-9, or validation from the Social Security Administration or the IRS if this was a second notice. Doing nothing is the one response that costs money, because if you do not collect and pay over the backup withholding you may become liable for the uncollected amount yourself.

Do I really have to withhold 24% from a contractor I already agreed to pay in full?

Yes, once the notice obligations bite, and this is what makes backup withholding different from every other tax a freelancer deals with. It is not your tax. It is an advance payment of the contractor's income tax that you are required to take out of the money you send them and remit to the IRS on their behalf. A $2,500 invoice becomes $1,900 to the contractor and $600 to the Treasury, reported to the contractor in box 4 of their Form 1099-NEC so they get credit for it on their own return. Contractors often push back hard, because from their side it looks like you are short-paying an invoice. The answer is that the obligation is imposed on you by section 3406 and the General Instructions for Certain Information Returns are explicit that a payer who does not collect and pay over backup withholding as required may become liable for any uncollected amount. Refusing to withhold does not protect the contractor's cash flow, it just moves the same 24% onto your own tax bill with penalties attached.

What is the difference between the first B notice and the second B notice?

The first B notice includes a Form W-9 and asks the payee to complete it. The second B notice must not include a W-9, because a second W-9 from the same person would just repeat the information the IRS has already rejected. Instead, the second notice tells the payee to obtain validation of their name and number directly from the issuing agency: a Social Security card from the Social Security Administration for an individual, or Letter 147C from the IRS for an entity operating under an EIN. In both cases the outer envelope must be marked conspicuously with wording such as IMPORTANT TAX INFORMATION ENCLOSED or IMPORTANT TAX RETURN DOCUMENT ENCLOSED. Which notice you send depends on how many CP2100 or CP2100A notices you have received for that account within three calendar years, which is why Publication 1281 tells payers to track the notices themselves — the IRS does not track it for you. You generally never have to send more than two B notices to the same account within three calendar years.

Where do I report backup withholding — Form 941 or Form 945?

Form 945, the Annual Return of Withheld Federal Income Tax, and never Form 941. Form 941 is for payroll withholding on employee wages; backup withholding is nonpayroll withholding and lives on its own annual return. Form 945 is due January 31 following the calendar year, extended to February 10 if every required deposit was made on time, and the two systems must not be mixed even for deposit purposes: you do not combine Form 945 amounts with Form 941 amounts when working out whether the $2,500 deposit threshold applies or whether you are a monthly or semiweekly depositor. There is a trap here for sole proprietors. Form 945 requires an EIN, the instructions say plainly not to use an SSN or ITIN on a form that asks for an EIN, and the name and EIN on Form 945 must match the name and EIN on the information returns reporting the withholding. A freelancer who has always filed 1099-NECs under a Social Security number needs to apply for an EIN before any of this works.

What are the penalties for filing a 1099 with a wrong TIN?

They are charged twice, because section 6721 penalises the incorrect information return filed with the IRS and section 6722 separately penalises the incorrect payee statement you gave the contractor. Each runs at $60 per return if you correct within 30 days of the due date, $130 if you correct by August 1, and $340 if you file after August 1 or never correct, with lower annual caps for small businesses whose average annual gross receipts for the three most recent tax years are $5 million or less. Intentional disregard is at least $680 per return with no maximum at all. There is no de minimis escape for this particular error: the General Instructions list a TIN, a payee's surname and any money amount as things that are never inconsequential, so a wrong TIN can never be argued away as a harmless typo. Two things do help. Sending a B notice in response to a CP2100 or CP2100A satisfies the annual solicitation requirement, which is what a payer relies on to avoid the penalty, and reasonable cause remains available if you can show the failure was beyond your control and that you acted responsibly before and after it.

Authoritative References

• IRS Publication 1281 — Backup Withholding for Missing and Incorrect Name/TIN(s)
• IRS — General Instructions for Certain Information Returns (Part N, Backup Withholding; Part O, Penalties)
• IRS — Instructions for Form 945, Annual Return of Withheld Federal Income Tax
• IRS — Taxpayer Identification Number (TIN) Matching
• IRC §3406 — Backup withholding
• IRC §6721 — Failure to file correct information returns
• IRC §6722 — Failure to furnish correct payee statements

Related reading: Schedule C Line 11, contract labor · Lines I and J, the 1099 filing questions · EIN vs SSN on Schedule C · Hiring a W-2 employee vs a 1099 contractor · What a CP2000 notice means

The W-9 You Can't Find Is the One This Costs You

Every deadline in this process runs off a document you collected months ago and filed somewhere. CentSense captures contractor paperwork and payment records with AI the day they arrive, keeps a searchable per-payee history, and exports a CPA-ready CSV — so "what TIN did they give me, and when?" is a search rather than an archaeology project. Free tier includes 10 AI scans per month; Solo is $5/month for unlimited scanning and mileage logging.

Start free →

This guide is general education for U.S. freelancers and Schedule C filers in 2026. It is not personalized tax advice. Penalty amounts under §6721 and §6722 are adjusted annually for inflation and the figures above are those for information returns required to be filed in 2026 — the year the 1099s behind a 2026 CP2100 notice were filed. Later filing years carry higher amounts, and the IRS publishes the current table at IRS.gov/payments/information-return-penalties rather than in the General Instructions. A CP2100 notice that arrives with contractors still being paid is worth taking to a CPA or EA while the 30-business-day clock still has room in it.