IRS Notice CP2100: Backup withholding notice (50+ mismatches)
Quick answerSent to payers (businesses that file 1099s): names and taxpayer ID numbers on some information returns don't match IRS records. CP2100 goes to payers with larger lists.
Letter / noticeCP2100
MeaningBackup withholding notice (50+ mismatches)
Action needed?Yes — see steps
What happens next
Send the first 'B' notice to each listed payee within 15 business days and start backup withholding if they don't respond.
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What you should do
- Compare the list to your records
- Send B notices and Form W-9 to listed payees
- Begin backup withholding (24%) 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 CP2100 mean?
Sent to payers (businesses that file 1099s): names and taxpayer ID numbers on some information returns don't match IRS records. CP2100 goes to payers with larger lists.
What should I do?
Compare the list to your records Send B notices and Form W-9 to listed payees Begin backup withholding (24%) where required
How long does it take?
Send the first 'B' notice to each listed payee within 15 business days and start backup withholding if they don't respond.
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.