IRS Notice CP2100A: Backup withholding notice (under 50 mismatches)
Quick answerLike CP2100, but for payers with a smaller number of name/TIN mismatches on information returns.
Letter / noticeCP2100A
MeaningBackup withholding notice (under 50 mismatches)
Action needed?Yes — see steps
What happens next
Send B notices to listed payees within 15 business days.
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What you should do
- Send B notices and Form W-9 requests
- Start backup withholding where required
Scam check: the IRS first contacts you by mail. Use only the phone numbers printed on your letter or on IRS.gov — never ones from a text, email or unofficial site.
Frequently asked questions
What does IRS Notice CP2100A mean?
Like CP2100, but for payers with a smaller number of name/TIN mismatches on information returns.
What should I do?
Send B notices and Form W-9 requests Start backup withholding where required
How long does it take?
Send B notices to listed payees within 15 business days.
Sources
- IRS: Understanding your IRS notice or letter
- IRS: Get Transcript
- Taxpayer Advocate Service (independent help inside the IRS)
Written by the editorial team and checked against the official sources above. See our editorial policy.
By the TranscriptCodes Editorial Team · Last reviewed 2026-11-12.