What Is IRS Letter 12C?

IRS Notices Explained
Written by Enrolled Agent
Reviewed by Enrolled Agent

Letter 12C means the IRS needs additional information or documentation to finish processing your tax return. It’s not an audit. It’s a request to provide specific forms or proof so the IRS can complete your filing and correctly calculate any refund or balance.

Quick Answer

IRS Letter 12C is a request for missing information. The IRS paused your return because something needs to be verified or added. Once you send what’s requested by the deadline on your letter, processing continues.

Good news: This is usually straightforward. Send the exact items listed in the letter and include the barcode/identifiers on every page you submit.

Why You Received Letter 12C

Missing or inconsistent forms (for example, reconciliation forms or schedules referenced on your return).
Income, credits, or dependents need verification before the return can be finalized.
Third-party information doesn’t fully match what was filed and the IRS needs proof to reconcile.
Identity or filing status details require confirmation.

Letter 12C is not a penalty notice and not a full audit. It’s a targeted request to complete processing accurately.

What Letter 12C Means

The IRS has identified specific items it cannot finalize without your response. The letter lists:

Exactly what documents or forms are needed.
Where to send them (fax or mail) and how to label them.
Your reply deadline (printed on the letter).

The sooner you respond with the correct items, the sooner the IRS can release your refund or finalize any balance due.

Documents the IRS Commonly Requests

Copies of W-2/1099 forms that support wages or other income.
Form 8962 and Form 1095-A (if reconciling health insurance premium tax credits).
Schedules supporting credits or dependents (e.g., child-related credits) and proof of eligibility.
Proof for withholding or estimated payments claimed.
Corrected or complete versions of missing schedules referenced on the return.
Documentation for identity/filing status if requested.

Only send what the letter asks for. Extra, unrelated documents can slow processing.

How to Respond (Step-by-Step)

Read the letter carefully. Highlight the exact items requested and the Response by date.
Gather documents. Make clear, legible copies. If a form is incomplete, fill it out fully before sending.
Label every page. Write your name, TIN, tax year, and include the barcode/notice number shown on the letter on each page.
Send by the method listed. If fax is offered, it’s typically faster. If mailing, use trackable mail and keep the receipt.
Keep a full copy. Save everything you send, plus the mailing or fax confirmation page.
Watch for updates. Processing resumes after the IRS receives what it needs. If nothing changes after a reasonable time, follow up.

Need the bigger picture? See our Complete Guide to Back Taxes in the U.S. for how notices, adjustments, and collections fit together.

If You Ignore Letter 12C

If you don’t respond, the IRS may process your return without the missing information—often reducing or denying credits, adjusting income, or holding a refund. In some cases the return cannot be processed and will remain delayed until the items are received.

Responding fully and on time protects your refund, prevents incorrect balances, and avoids follow-up notices.

How Polaris Can Help

Polaris Tax & Accounting handles Letter 12C responses nationwide. Our Enrolled Agents identify exactly what the IRS requested, assemble the right documents, complete any missing forms, and submit a clean, properly labeled package—so your return moves forward.

If prior filings or credits need correction, we fix them and safeguard your position going forward.

Your Next Step: Get a precise, on-time response to Letter 12C. Schedule a consultation.

Related Resources

FAQs

Is Letter 12C an audit?

No. It’s a request for missing information so the IRS can finish processing your return.

How fast should I respond?

Use the deadline printed on your letter. Sooner is better—processing resumes after the IRS receives complete documentation.

Should I mail or fax?

Follow the instructions on your letter. If fax is available, it’s often the fastest. Keep transmission or mailing proof.

Do I send originals?

No—send clear copies unless the letter specifically asks for originals.

What if I disagree with what the IRS is asking for?

Respond in writing with an explanation and supporting documents. Professional representation helps you avoid delays and protect credits.