IRS CP2100 / CP2100A: what it means and what to do
As a payer who filed information returns such as 1099s, you included payee names or taxpayer identification numbers (TINs) that were missing, obviously incorrect, or didn't match IRS records. You may need to start backup withholding. A CP2100 goes to payers with 50 or more such returns, and a CP2100A to payers with fewer than 50. This summary is drawn from the IRS page for the CP2100 / CP2100A, last checked on October 13, 2026.
Why you received a CP2100 / CP2100A
- A payee TIN on your information returns was missing
- A payee TIN was obviously incorrect (not nine digits, or contains non-numeric characters)
- A payee name and TIN combination didn't match IRS records
What to do
- For missing or obviously incorrect TINs, start backup withholding right away if you haven't already
- Ask the payee for their TIN, up to three times (initial, first annual and second annual requests), to avoid a penalty
- For mismatched TINs, compare your records to the notice
- If your records match the notice, send the appropriate B notice to the payee
- If your records don't match, correct your records. Don't call or write the IRS about the correction
- Confirm your mailing address with the IRS, and file Form 8822-B to change it
Deadline: Begin backup withholding on missing or obviously incorrect TINs immediately. For mismatched TINs where the payee doesn't respond, begin backup withholding on future payments no later than 30 business days after you receive the notice. Stop no later than 30 calendar days after you receive the payee's TIN.
Get your records together first
Most notices come down to matching what the IRS has on file against your own records. Before you reply, pull the return the notice refers to, the bank statements and income forms for that year, and any payment confirmations. If your books are reconciled to the bank, that comparison takes minutes instead of days.
Source and verification
IRS: Understanding your CP2100 or CP2100A notice →
Last verified against that page on October 13, 2026. This is general information, not advice for your situation. The notice itself is the authority on your amounts and dates. Talk to a CPA or enrolled agent if the amounts are large or you are unsure.
Related
- All IRS notices explained
- IRS CP162 — The IRS charged your partnership or corporation a penalty because the return was not filed electronically as required.
- IRS CP575 — The CP575 is a digital notice confirming your business's Employer Identification Number (EIN).
- IRS CP136 — Your Form 941 tax deposit schedule for next year may change.
- Find an accountant — for help responding.
Frequently asked questions
What is an IRS CP2100 / CP2100A notice?
As a payer who filed information returns such as 1099s, you included payee names or taxpayer identification numbers (TINs) that were missing, obviously incorrect, or didn't match IRS records. You may need to start backup withholding. A CP2100 goes to payers with 50 or more such returns, and a CP2100A to payers with fewer than 50.
How long do I have to respond to a CP2100 / CP2100A?
Begin backup withholding on missing or obviously incorrect TINs immediately. For mismatched TINs where the payee doesn't respond, begin backup withholding on future payments no later than 30 business days after you receive the notice. Stop no later than 30 calendar days after you receive the payee's TIN. Check the date printed on your own notice, which is the one that applies to you.
What is the difference between a CP2100 and a CP2100A?
A CP2100 goes to payers with 50 or more incorrect information returns, and a CP2100A goes to payers with fewer than 50. The instructions are the same.
How do I backup withhold?
Follow Publication 15. Backup withholding is currently 24% of payments and is reported on Form 945, filed under the same name and EIN used on the information returns.
What if a payee sends me a corrected TIN?
Don't send it to the IRS. Update your records and stop backup withholding on future payments.
How can I verify TINs?
Most Form 1099 payers can apply for the IRS TIN Matching program.
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Authoritative sources
US tax rules change every filing season. Always verify the current position with the official sources below before filing.
- IRS — irs.govInternal Revenue Service. Forms, publications, due dates, and current-year thresholds for federal income tax, payroll tax, and 1099 reporting.
- IRS — Forms & InstructionsCanonical PDF forms (W-4, W-9, 1099-NEC, 1040-ES, 941, 940, W-2, W-3) with current-year instructions.
- SSA — Business Services OnlineSocial Security Administration portal for W-2 / W-3 e-filing, EIN verification, and AccuWage validation.
- Streamlined Sales Tax — streamlinedsalestax.orgMulti-state Streamlined Sales and Use Tax Agreement (SSUTA) — registration in 24 SST member states with one application.
- Tax Foundation — Sales Tax & NexusIndependent state-by-state research on sales tax rates, economic nexus thresholds, and franchise / margin tax structures.
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