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Got a CP2100? A plain-English guide to B notices
What the IRS letter means, what you have to send and when, and how backup withholding works. Enter the date on your notice to get your deadlines.
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Short answer
A CP2100 or CP2100A notice lists payees whose name and TIN on your 1099s were missing or didn't match IRS records. For each incorrect TIN, send a B notice within 15 business days of the notice date (or the date you received it, if later); if you don't get a correct TIN, start backup withholding at 24% no later than 30 business days after receiving the notice. A second notice for the same payee within three calendar years needs a second B notice, and the payee must prove the TIN with a Social Security card, IRS Letter 147C (EIN) or Letter 685C (ITIN).
- Sent twice a year: October and the following April
- CP2100A: fewer than 50 errors; CP2100: 50 or more
- Backup withholding is reported on Form 945 and box 4 of the 1099
- A CP2100 isn't a penalty notice; a proposed penalty comes on Notice 972CG
Last reviewed against IRS Publication 1281 (Rev. 12-2023) and the IRS CP2100 notice page.
B notice deadline calculator
What a CP2100 is, and why you got one
After you file 1099s, the IRS compares every payee's name and TIN with its records. A CP2100 or CP2100A notice lists the ones that didn't line up: TINs that were missing, weren't nine digits, or don't match the name. The IRS sends these twice a year, in October and the following April.
The notice itself doesn't cost you anything. It starts a clock. The IRS expects you to contact each listed payee, get a correct TIN, and withhold tax if you can't. Doing that on time is your protection against penalties for incorrect TINs.
Step by step
- Compare the list with your records. For each account on the notice, check your current vendor file. If the payee has already given you a corrected TIN since you filed, or you no longer pay them, note that and keep your records. You still have to act on accounts that are open and unchanged.
- Sort missing TINs from incorrect ones. Missing TINs don't get a B notice. You should already be backup withholding and asking for the TIN. Incorrect TINs (name and number don't match) go through the B notice process below.
- Mail the B notice within 15 business days. For a first-time payee, send the first B notice with a blank Form W-9 and a reply envelope. For a payee listed again within three calendar years, send the second B notice. Use the IRS wording from Publication 1281; you can add your own cover letter, and our W-9 request generator has a plain-language mismatch letter you can adapt.
- Collect the fix. After a first B notice, a signed W-9 with a corrected (or confirmed) TIN is enough. After a second B notice, it isn't: an individual needs to give you a copy of their Social Security card, and a business needs an IRS Letter 147C showing its name and EIN.
- Backup withhold within 30 business days if nothing valid comes back. Withhold 24% of every reportable payment to that payee until they provide what's needed. Once they do, stop within 30 calendar days.
- Fix your records before next year's filing. Update the payee's name and TIN, check the name against the IRS name control rules, and consider running IRS TIN Matching before you file again, so the same payee doesn't land on next year's notice.
First vs. second B notice at a glance
| First B notice | Second B notice | |
|---|---|---|
| When | Payee's first appearance on a CP2100 | Same payee listed again within 3 calendar years |
| Send within | 15 business days | 15 business days |
| Include | B notice text, blank W-9, reply envelope | B notice text, reply envelope |
| What fixes it | A signed, certified W-9 | A copy of the Social Security card (SSN) or IRS Letter 147C (EIN) |
| If nothing valid comes back | Backup withhold 24% within 30 business days | Backup withhold 24% within 30 business days |
Backup withholding in two minutes
Backup withholding means holding back 24% of a reportable payment and sending it to the IRS instead of to the payee, a bit like income tax withholding on wages. You deposit it with your other federal tax deposits, report it in box 4 of the payee's 1099 (that 1099 is required whatever the amount), and report the year's total on Form 945. It's a credit for the payee on their own tax return, so they don't lose the money. They just get it back later.
The best way to avoid all of this is upstream: collect a W-9 before the first payment, check the TIN, and confirm the name and TIN with TIN Matching before you file.
Related tools
- Find why a name and TIN don't match with the name control generator.
- Ask for a corrected W-9 with the W-9 request letter.
- How withholding works day to day: backup withholding guide.
- Fixing the 1099 itself: the 1099 correction guide.
Sources
- IRS Publication 1281, Backup Withholding for Missing and Incorrect Name/TINs (Rev. 12-2023)
- IRS: Understanding your CP2100 or CP2100A notice
- IRS: Backup withholding "B" program
- IRS: About Form 945, Annual Return of Withheld Federal Income Tax
- IRS Publication 1099, General Instructions for Certain Information Returns (part N, backup withholding)
Questions
CP2100 and B notice questions
What is a CP2100 notice?
A CP2100 or CP2100A is a notice the IRS sends to businesses that filed information returns, usually 1099s, where a payee's name and TIN were missing or didn't match IRS records. It lists each problem account. It isn't a penalty notice. It's the IRS telling you to start the B notice process. Which one you get depends on how many problem accounts there are: a paper CP2100A for fewer than 50, a paper CP2100 for 50 to 249, and a CP2100 data file on CD or DVD for 250 or more.
What is a B notice?
A "backup withholding" notice that you, the payer, send to each payee listed on a CP2100. It tells them their name and TIN don't match IRS records and that you'll have to withhold 24% of future payments unless they fix it. The IRS publishes the required wording for both the first and the second B notice in Publication 1281.
How long do I have to send a B notice?
Within 15 business days of the date on the CP2100 or the date you received it, whichever is later. If the payee doesn't send back what's needed, you must start backup withholding within 30 business days of that same date.
What's the difference between a first and second B notice?
A first B notice goes to a payee the first time they appear on a CP2100; they can fix it by returning a signed W-9. If the same payee shows up again within three calendar years, you send a second B notice, and this time a W-9 isn't enough. An individual has to give you a copy of their Social Security card; a business has to give you an IRS Letter 147C confirming its name and EIN. (ITINs are confirmed with IRS Letter 685C.)
What is the backup withholding rate?
24% of each reportable payment. You deposit it like other withheld federal tax, report it in box 4 of the payee's 1099, and report the year's total on Form 945.
Do I need a B notice for a missing TIN?
No. If the TIN was missing altogether, you should already have been backup withholding and soliciting the TIN. B notices are for TINs that were provided but are incorrect, meaning the name and number don't match.
Does a CP2100 mean I'll be penalized?
Not by itself. Penalties for incorrect TINs come separately (a proposed penalty notice is Notice 972CG). Following the B notice and solicitation rules is what lets you show reasonable cause and avoid them.
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