CP2100/CP2100A & “B” Notices: Your 15-Day and 30-Day Action Plan

What this notice means

A CP2100 or CP2100A notice means the IRS found some 1099s with missing or incorrect Name/TIN details. You compare the IRS list to your vendor list, then take action. The IRS sends CP2100 when there are 50+ returns with errors and CP2100A when there are <50 the steps are the same. IRS

If a TIN is missing or obviously wrong (not 9 digits or not numbers), begin backup withholding right away while you ask for the TIN. IRS

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The plan at a glance

• Within 15 business days: send the correct “B” Notice
  – First B Notice (include Form W-9) if this is the first time in 3 years for that account
  – Second B Notice (no W-9) if you’ve received a second notice for the same account within 3 years
  – Mark the envelope: “IMPORTANT TAX INFORMATION ENCLOSED” (or “IMPORTANT TAX RETURN DOCUMENT ENCLOSED”) IRS
• By 30 business days: if no response, start backup withholding on payments to that payee (you may start sooner).
  – Current rate: 24%
  – When they send what’s required, stop within 30 calendar days (W-9 for First B; SSA/IRS validation for Second B). IRS+1

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Step-by-step (plain language)

1) Match the IRS list to your records (Day 0–2)

• Sort vendors into Missing TIN vs Incorrect TIN.
• If the issue was your typo, just fix your records—do not send a B Notice. IRS

2) Send the right B Notice (by Day 15 business days)

• First B Notice: send within 15 business days and include Form W-9. Envelope must show the required wording above. IRS
• Second B Notice: send within 15 business days but do not include a W-9. The payee must get SSA/IRS validation (e.g., SSN card or IRS Letter 147C). IRS
• If you receive two CP2100/CP2100A notices in the same calendar year, you don’t have to mail a Second B Notice. Track which one is first vs second for each account. IRS

3) Begin/stop backup withholding (by Day 30 business days)

• If the payee doesn’t respond in time, start backup withholding no later than 30 business days after you got the notice (you can start earlier).
• Rate is 24%. Stop within 30 calendar days after you receive a valid W-9 (first notice) or SSA/IRS validation (second notice). IRS+1

4) If mail comes back “undeliverable”

• Begin backup withholding, try to get the correct address, and keep the returned mail for 3 years to track the “two-in-three-year” rule. IRS

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Annual TIN solicitations (so you avoid penalties)

• Missing TINs:
  – Ask at onboarding/transaction (initial)
  – First annual by Dec 31 (or Jan 31 if the account opened the prior December)
  – Second annual by Dec 31 of the next year if still missing IRS
• Incorrect TINs:
  – Sending a B Notice on time counts as the annual solicitation for penalty relief on that return. IRS

For penalty relief based on reasonable cause (you acted responsibly, had mitigating factors, etc.), see Publication 1586. IRS

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Quick FAQ

When does the IRS send these notices?
Typically twice a year October and the following April. IRS

What’s the difference between CP2100 and CP2100A?
Only the number of returns with errors: CP2100 (50+), CP2100A (<50). Steps are the same. IRS

What payments are subject to backup withholding?
Many 1099-type payments can be subject if a TIN is missing/incorrect or the IRS instructs you to withhold. Rate is 24%. IRS+1

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How to reduce CP2100s next season (and stress)

• Collect W-9s upfront with automatic reminders.
• Save W-9 PDFs with a submission history (tamper-evident record).
• Optional: If you use QuickBooks, connect it to auto-import vendors.
• Use USPS Address Validation to cut returned mail; watch audit-trail flags for early fixes.
• Keep clean exports for smooth 1099 prep.

With GetW9, this is turnkey: fewer notices, less chasing, better records.

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Disclaimer

This article is informational and not tax or legal advice. Please consult your CPA for guidance on your situation.

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Sources

• IRS: Understanding your CP2100/CP2100A Notice (what it is, timing, differences, 24% reference). IRS
• IRS: Publication 1281 (15-day B-Notice, envelope wording, 30-day start/stop, annual solicitation & tracking). IRS
• IRS: Backup Withholding (current 24% rate + overview) and Topic 307. IRS+1
• IRS: Publication 1586 (reasonable-cause penalty relief). IRS

Avoid CP2100 headaches next season automate W-9 collection with GetW9: requests, reminders, USPS-validated addresses, and tamper-evident W-9 PDFs with a submission history. Start free → getw9.tax