IRS letter help
What to do about a CP2100 notice
You got a CP2100, so some 1099s you filed show payee numbers the IRS cannot match.
Send each listed payee a B notice, and start 24% backup withholding no later than 30 business days after you got it.
Send your payee list and B notices through the form, and have them checked before those 30 business days run out.
Which numbers matter?
30 business days
You must start backup withholding on payees who do not answer by then, counted from the day you got the notice.
Write the day your CP2100 arrived on the notice and count forward.
24%
You hold back 24% of each payment to a payee who has not fixed the number.
Report what you hold back on Form 945 under the same EIN as your 1099s.
30 calendar days
Once a payee sends a correct number, you have 30 calendar days to stop withholding.
Update your payment system as soon as a correct number arrives.
Get your CP2100 payee list checked
Your CP2100 starts a count of 30 business days from the day you got it.
Start late and you miss the IRS rule, so a licensed tax professional can check each payee and B notice.
Send your CP2100 payee list through the form, or call now to sort out the mismatched numbers.
Call 855-964-5291What happens when you call
- You call during business hours and say which letter or bill you have.
- A licensed tax professional asks for the date, the amount and the tax years on the letter.
- You hear your options for this notice and decide what to do. Nothing is filed without your yes.
A licensed tax professional answers, not the IRS. The call costs nothing, and you give up nothing by calling. IRS Code Lookup is a private tax help service.
Would you rather send your CP2100 details?
Your CP2100 lists each payee whose name and number did not match, so sending it shows exactly which 1099s need work.
Add your own records for those payees so a licensed tax professional can tell which B notice each one needs.
What is it?
The IRS sends a CP2100 when a payer filed 50 or more returns with errors, and a CP2100A for fewer than 50. The instructions are the same. They go out twice a year, in October and April, per the IRS CP2100 page.
What do I send my payees?
- Compare the list on the notice with your records.
- If they match, send the payee the right "B" notice asking for a correct number.
- If the payee does not answer, start backup withholding no later than 30 business days after you got the CP2100.
- When the payee sends a correct number, stop backup withholding within 30 calendar days.
What is backup withholding?
The rate is 24% of each payment. Report it on Form 945 under the same EIN you used on the information returns. Payees who give no number at all, or an obviously wrong one, get backup withholding on every payment until they supply it.
Mavis pays six freelance designers. Two numbers on her CP2100 did not match. She sent B notices the next week and set her payment app to hold 24% for those two.
What should you read next?
Questions people ask
What is the difference between CP2100 and CP2100A?
CP2100 goes to payers with 50 or more returns with errors; CP2100A to those with fewer than 50.
What is the backup withholding rate?
24% of each payment to the payee.
When does the IRS send CP2100 notices?
Twice a year, in October and April.
How can I get a copy of a CP2100?
Call 866-455-7438, toll-free.
Sources
- Understanding your CP2100 or CP2100A notice. Published by irs.gov.
Last checked October 2026
What to do now
- Mark the day your CP2100 arrived and count 30 business days forward.
- Compare each listed name and number with your own payee records.
- Mail the right B notice to every payee whose records match the list.
- Start 24% backup withholding for payees who do not answer, and report it on Form 945.
Send your CP2100 payee list through the form, or call now to sort out the mismatched numbers.
A licensed tax professional answers, not the IRS. The call costs nothing, and you give up nothing by calling. IRS Code Lookup is a private tax help service.