Letter 12C is a request for missing information. The IRS started processing your individual income tax return and found something it needs before it can finish, such as a form, a schedule, or proof of an amount you reported. It is not an audit and it is not a bill. Your return, and any refund, is simply on hold until you reply. Most people resolve a Letter 12C with one mailed or faxed response.
Why you got a Letter 12C
The IRS says the information it needs could be:
- Missing or corrected forms or schedules that support entries on your Form 1040 or 1040-SR.
- Verification of income, withholding and credit amounts.
- Verification of taxpayer identification numbers or Social Security numbers.
A common case: a missing Form 8962
Letter 12C is often about health coverage. If you or a family member had insurance through HealthCare.gov or a state Health Insurance Marketplace, the Marketplace may have paid advance payments of the premium tax credit (APTC) directly to your insurance company to lower your monthly premium. When that happens, you must file Form 8962, Premium Tax Credit, with your return. Form 8962 compares the advance payments with the credit you actually qualify for, based on your real household income and family size. This is called reconciling.
The IRS sends Letter 12C when the Marketplace reported advance payments for you but your return didn't include Form 8962.
What the Letter 12C says
Look for:
- The tax year of the return.
- Exactly what the IRS needs. The letter lists the missing items.
- The response deadline. The IRS asks you to send the information within 20 days.
- How to reply, including a mailing address and a fax number.
Example: the 20-day window. If your Letter 12C is dated October 1, 2026, 20 days later is October 21, 2026. If you can't meet the deadline, call the number on the letter before it passes rather than letting it lapse.
What to do
- Read the letter carefully and list every item it asks for.
- Gather the documents. For a premium tax credit letter, that means a copy of your Form 1095-A, Health Insurance Marketplace Statement, and a completed Form 8962. For other letters, it may be a missing schedule, a W-2 or 1099, or proof of a credit.
- Respond even if you disagree. Include a clear written explanation of what you think is wrong. If you didn't buy a Marketplace plan, say so.
- Send your reply within 20 days to the address on the letter, or fax it to the number on the letter. If you use an online fax service, check its privacy and security policies.
- Keep copies of everything and proof of when you sent it.
Do not file Form 1040-X, Amended U.S. Individual Income Tax Return, in response to Letter 12C. The IRS says it will use the information you send to process your original return.
Getting your Form 1095-A
The Marketplace must send Form 1095-A by January 31 for the prior coverage year. If you didn't get one, log in to your HealthCare.gov or state Marketplace account, or contact the Marketplace directly. The IRS says it can't answer questions about what's on your 1095-A, reissue lost forms or issue corrected ones. If you had more than one Marketplace policy, you'll get a Form 1095-A for each.
For premium tax credit questions, the IRS lists 866-682-7451, extension 568.
After you respond
If you're owed a refund, the IRS says it will send it about 6 to 8 weeks after it receives all the information it needs. Your reconciled amount could raise or lower your refund. If the advance payments were more than the credit you qualify for, you may have to repay some or all of the difference. If they were less, you get the extra credit. You can track the status with Where's My Refund or your IRS Online Account.
If the IRS changes your return after reviewing your reply, expect a separate notice explaining the change. Our CP12 page covers one common example, a change that affects your refund.
What happens if you ignore it
Your return stays on hold, so any refund is delayed. For premium tax credit letters, there's another cost: the IRS says that if you don't reconcile, you won't be eligible for advance payments of the premium tax credit or cost-sharing reductions to help pay for Marketplace coverage in the following calendar year. That could make your health insurance much more expensive.
Is this notice real?
A real Letter 12C comes by U.S. mail and asks you to mail or fax documents to the IRS. It doesn't ask for payment by phone, gift card or wire transfer, and the IRS doesn't start contact by email, text or social media. To check, call the IRS at a number listed on irs.gov, or look at your account in your IRS Online Account. See our IRS scams guide.
Frequently asked questions
How long do I have to respond to Letter 12C?
The IRS asks you to send the information within 20 days. Use the date on your letter to count.
Should I file an amended return to add Form 8962?
No. The IRS says not to file Form 1040-X. Send Form 8962 and a copy of your Form 1095-A with your reply to the letter.
I didn't have Marketplace insurance. What should I do?
Respond anyway and tell the IRS you didn't buy a Marketplace policy. Include any explanation that helps. If someone may have used your information to enroll, read our tax identity theft guide.
Will I owe money after I file Form 8962?
Possibly. If your actual income was higher than the Marketplace estimated, your advance payments may have been more than your credit, and you may have to repay some of it. If your income was lower, you may get a bigger credit. The repayment rules depend on the tax year, so check the Form 8962 instructions for your year or ask a tax professional.
Who can help me with Form 8962?
Free help may be available through IRS Volunteer Income Tax Assistance (VITA) sites if you qualify. A Low Income Taxpayer Clinic or the Taxpayer Advocate Service can help if you're stuck. See our individual taxpayers hub for more guides.
Sources
IRSV.com is an independent guide and is not affiliated with the IRS. This page is general information, not tax or legal advice. Rules change; confirm details on IRS.gov or with a tax professional. Found an error? Tell us.