A 12C letter from the IRS is a request for information the agency needs to finish processing your tax return. It isn’t an audit and it isn’t a bill. Something on your return is missing, unclear, or unreadable, and until you send what the letter asks for, your return sits on hold and your refund won’t move.
Why the IRS Sent It
The letter itself will spell out what triggered it. The usual reasons fall into a handful of categories:
- A required form or schedule wasn’t attached. The most common version is a missing Form 8962 (Premium Tax Credit) when the Marketplace reported advance premium payments for someone in your household. Missing Forms 1095-A and Schedule 1 also come up often.
- The IRS wants documentation of the income you reported, such as W-2s or 1099s.
- You claimed a credit or deduction, and the return doesn’t include enough information to confirm it.
- A Social Security number or ITIN on the return is missing, illegible, or doesn’t match IRS records.
- Part of the return was damaged or unreadable during processing.
The Premium Tax Credit situation catches a lot of filers. If anyone in your household had Marketplace coverage with advance subsidies, you have to file Form 8962 reconciling those payments. Leave it off and a 12C is almost guaranteed.
Confirm the Letter Is Real Before You Send Anything
The IRS makes first contact by mail, never by email, text, or social media. That doesn’t rule out a scam letter in your mailbox, though. Before you send documents anywhere, log in to your IRS Online Account at irs.gov and check whether the notice appears there. You can also call IRS customer service using the number listed on the IRS website, not one printed on the letter you’re trying to verify.1Internal Revenue Service. Ways to Tell if the IRS Is Reaching Out or if It’s a Scammer
What the Letter Asks For
Read the letter line by line. Every 12C states exactly what the IRS needs, and you should respond only to what it lists.2Taxpayer Advocate Service. Letter 12C Typical requests are copies of W-2s or 1099s, a form or schedule that was left off the original return, or documentation supporting a specific credit. If the letter asks for Form 8962, you’ll complete it and send it along with the Form 1095-A from your Marketplace.3Internal Revenue Service. Reconciling Your Advance Payments of the Premium Tax Credit
One thing the Taxpayer Advocate Service specifically warns against: don’t send a copy of your entire tax return unless the letter tells you to. Extra documents slow processing and create confusion.2Taxpayer Advocate Service. Letter 12C
How to Respond and by When
You have 20 days from the date printed on the letter to send your response.4Internal Revenue Service. Understanding Your Letter 12C The clock runs from the notice date, not the day the envelope arrived, so if it sat in transit for a week your working window is already shorter. Don’t let it wait.
There are three ways to send what the IRS asked for:
- The IRS Document Upload Tool at irs.gov. You’ll need either the access code from your letter or the letter number, along with your name and Social Security number. This is the fastest option and gives you immediate confirmation of receipt.
- Fax, using the number printed on the letter. Keep the transmission confirmation.
- Mail, to the address on the letter. Use certified mail with return receipt requested so you have proof of delivery.
Whichever route you take, make copies of everything before it leaves your hands, and include a copy of the 12C letter itself so the IRS can match your documents to your case. Questions about what the letter wants go to the toll-free number in the top right corner of the letter.2Taxpayer Advocate Service. Letter 12C
What Happens If You Don’t Respond
Ignoring the letter doesn’t make it go away. The IRS will process your return without the missing information, which almost always means disallowing whatever credit or deduction it couldn’t verify. That can shrink your refund or turn it into a balance due. Once there’s a balance, penalties and interest start running, and the Taxpayer Advocate Service recommends paying as much as you can by the original due date to limit those charges.2Taxpayer Advocate Service. Letter 12C If you’ve already missed the 20 days, send the information anyway. A late response is still better than none.
When Your Refund Will Arrive
Once the IRS has your complete response, plan on about six to eight weeks for your refund.4Internal Revenue Service. Understanding Your Letter 12C That window starts when the IRS receives your documents, not when you send them, and if your response is incomplete and the agency has to contact you again, the clock resets. If more than eight weeks go by with no refund and no follow-up letter, call the number on your original 12C.