A CP2100 or CP2100A notice is the IRS telling you that a name and taxpayer identification number (TIN) on a 1099 or W-2G you filed do not match Social Security Administration or IRS records. You must compare the notice against your files, send backup withholding notices (B-Notices) to the affected payees, and start backup withholding on future payments if they do not respond with a corrected W-9 within 30 business days.
Key Takeaway: If you receive a CP2100 or CP2100A notice, you have 30 business days to send a B-Notice to each listed payee and begin backup withholding if they don’t respond with a corrected W-9. Missing this window can trigger penalties and ongoing withholding headaches.
What It Is
The IRS sends a CP2100 or CP2100A notice after it runs your filed 1099 or W-2G forms through its TIN matching system. The system checks each payee name and TIN against SSA and IRS databases. When a name and number don’t line up, the IRS flags the mismatch and mails you a list of the affected payees.
CP2100 notices go to larger filers, usually those who submitted 250 or more information returns with errors. CP2100A notices go to smaller filers with fewer mismatches. Both notices carry the same requirements. Only the volume of listed errors differs.
The notice itself is not a penalty. It’s a warning that gives you a chance to fix the problem before the IRS assesses one. Ignoring it, though, can lead to real financial consequences down the road.
The IRS mails these notices in two rounds each year, typically in September and again in the spring. Filers who submit information returns for tax year 2026 should expect any related CP2100 notices to arrive during the 2027 filing season, so plan your response process well before those mailings land.
Who It Applies To
This notice applies to any business that files 1099-NEC, 1099-MISC, 1099-INT, 1099-DIV, 1099-B, or W-2G forms with incorrect payee information. Small businesses, nonprofits, contractors, and financial institutions all receive these notices when their filed data doesn’t match IRS records.
You’re most likely to see one if a contractor gave you a wrong Social Security number, misspelled their legal name, or used a name that doesn’t match what the IRS has on file for their business entity. Sole proprietors who mix personal and business names on forms often trigger these mismatches.
Bookkeepers and accountants who file on behalf of clients also need to watch for these notices. The notice goes to the filer of record, so your firm may need a process for forwarding it to the right client quickly.
Landlords who issue 1099s to property managers, staffing agencies that pay placed workers, and gig platforms that pay independent contractors all fall into this same category. Any organization that files information returns with the IRS can end up on the receiving end of a CP2100 notice.
Requirements
Once you get a CP2100 or CP2100A notice, you must act within 30 business days. First, compare the listed names and TINs against your records to confirm the notice is accurate. Sometimes a typo on your end caused the mismatch, and you can correct it without contacting the payee.
If your records match what you originally filed, you must send a B-Notice to the payee. The IRS provides two versions. A “First B-Notice” goes to a payee who has not appeared on a CP2100 notice in the past three years. A “Second B-Notice” applies if the same payee triggered a notice in one of the prior three years.
Each B-Notice must ask the payee to provide a corrected Form W-9 (for the first notice) or verify their TIN directly with the IRS or SSA (for the second notice). If the payee does not respond within 30 business days, you must begin backup withholding at the current rate of 24% on future payments to them.
You also need to keep records showing you sent the B-Notice and tracked the response. These records protect you if the IRS later questions whether you met your compliance obligations. Keep copies of the notice, your outgoing B-Notice letter, the mailing date, and any reply you receive from the payee for at least four years.
Common Mistakes
Many business owners assume the CP2100 notice is an automatic penalty notice and either panic or ignore it entirely. Both reactions cause problems. The notice is a compliance opportunity, not a bill, but it does require prompt action.
Some filers send a generic email instead of the IRS-required B-Notice format. The B-Notice needs specific language and must include a blank Form W-9. A casual email asking someone to “double check their tax info” doesn’t meet the requirement.
Other filers forget to start backup withholding when a payee doesn’t respond in time. Skipping this step can shift the tax liability back onto your business if the IRS later determines the payee underreported their income.
Missing the 30-business-day window is another frequent error. Business owners set the notice aside during a busy season and lose track of the deadline. This delay can result in penalty exposure for continued filing with an unverified TIN.
A less obvious mistake is sending a First B-Notice when a Second B-Notice was actually required. Filers who skip the step of checking their own three-year history end up asking for the wrong document, which restarts the clock and delays real compliance.
Best Practices
Build a standard process for handling every CP2100 or CP2100A notice the moment it arrives. Assign one person or team to open IRS mail related to information returns so nothing sits unread in a pile.
Collect a completed Form W-9 from every new contractor or vendor before you issue their first payment. This single habit prevents most TIN mismatches before they start. Store these forms securely and update them whenever a contractor changes their business name or entity type.
Use the IRS TIN Matching Program to verify names and numbers before you file your 1099s each year. This free service catches most mismatches early, well before the IRS sends a CP2100 notice.
Track every B-Notice you send and set calendar reminders for the 30-business-day response window. A simple spreadsheet with payee name, notice date, and response deadline keeps your team accountable and prevents missed deadlines.
Review your vendor list each fall, before the notices for that filing year typically arrive, so you already know which payees carry incomplete or unverified information.
How WageFiling Helps
WageFiling checks payee names and TINs against IRS records before you submit your 1099 forms, which cuts down on the mismatches that trigger a CP2100 notice in the first place. Our platform flags likely errors so you can fix them before filing instead of after.
If you do receive a notice, WageFiling stores your original filing data in one place, so you can quickly confirm whether the mismatch came from your side or the payee’s. This saves hours of digging through spreadsheets and old files during a tight response window.
Our support team can also walk you through the B-Notice and backup withholding process step by step, so you meet every IRS deadline without guesswork. For the 2027 filing season, we’re building reminders into the platform so you don’t lose track of the 30-business-day clock once a notice arrives.
Conclusion
A CP2100 or CP2100A notice signals a TIN mismatch, not an automatic penalty. Respond within 30 business days by verifying your records, sending the correct B-Notice, and starting backup withholding if the payee doesn’t reply. Build good habits now, like collecting W-9s upfront and running TIN Matching before you file, and you’ll rarely see one of these notices again.
If you’re unsure whether a notice you received needs a First or Second B-Notice, check your filing history from the past three years first. Getting this step right prevents you from sending the wrong form and restarting the response clock unnecessarily.
Treat every CP2100 notice as a short-deadline project, not routine mail. A quick response protects your business and keeps your relationship with contractors on solid ground.
For more on preventing TIN issues at the source, see our guide on what happens when a contractor or vendor refuses to provide a W-9. You can also review the IRS’s own guidance on understanding your CP2100 or CP2100A notice for the full technical requirements.
Frequently Asked Questions
How long do I have to respond to a CP2100 or CP2100A notice?
You have 30 business days from the notice date to send a B-Notice to each listed payee. If the payee does not return a corrected W-9 or verify their TIN within that window, you must start backup withholding on their future payments.
What’s the difference between a First and Second B-Notice?
A First B-Notice applies when the payee has not appeared on a CP2100 notice within the past three years, and it asks for a corrected Form W-9. A Second B-Notice applies when the same payee triggered a notice again within that three-year window, and it requires the payee to verify their TIN directly with the IRS or SSA instead of just resubmitting a W-9.
Will I owe a penalty just for receiving a CP2100 notice?
No. The notice itself is not a penalty. It’s a warning that gives you time to correct the mismatch. Penalties can follow if you ignore the notice, skip the required B-Notice, or fail to start backup withholding after a payee misses the response deadline.
Disclaimer: This article is for informational purposes only and should not be considered tax, legal, or accounting advice. Consult a qualified tax professional regarding your specific situation.
