Two common “we’re looking at your return” notices behave very differently:
- CP05 — the IRS is reviewing your return (income, withholding, or credits) and holding your refund. Usually you don’t need to do anything unless they follow up; it just takes time (often up to ~60 days).
- Letter 12C — the IRS needs specific information to finish processing (e.g., a missing form, proof of withholding, or Form 8962 for Marketplace insurance). This one requires a response, by the deadline, or your return/refund stalls.
Deadline: CP05 — none unless they ask. Letter 12C — respond by the date on the letter (commonly about 20 days) with exactly what they request.
What to do
- CP05: wait the stated period. Make sure you can support your income, withholding, and credits if asked. If it drags well past the timeframe, call the number on the notice or contact the Taxpayer Advocate.
- Letter 12C: send exactly the document(s) requested — nothing missing, nothing extra — using the fax number or address on the letter.
The letter (responding to Letter 12C)
[Your name]
[Address]
[City, State ZIP]
[Daytime phone]
[Date]
Internal Revenue Service
[Use the address/fax on your Letter 12C]
Re: Letter 12C - information requested to process my return
Name: [Your name] SSN/ITIN: [xxx-xx-1234]
Tax year / form: [year / 1040] Letter date: [date]
To whom it may concern:
I am responding to Letter 12C regarding my [year] return. You requested
[describe exactly what they asked for]. Enclosed is the requested information:
- [e.g. "Form 8962 (Premium Tax Credit) with a copy of Form 1095-A"]
- [e.g. "copies of W-2/1099 supporting the withholding claimed"]
- [the specific item(s) requested]
Please use this to finish processing my return and release any refund due. My
return otherwise stands as filed. Please confirm receipt.
Sincerely,
[Signature]
[Printed name]
How to send it
For Letter 12C, respond by the deadline using the fax or address on the letter (fax is often fastest for 12C), and include a copy of the letter so it’s matched to your file. Keep copies. For CP05, no letter is needed unless they request information.
Notes. Don’t send your whole tax file in response to a 12C — send only what’s asked, or you can slow things down. A held refund (CP05) is frustrating but normal; if it causes hardship, the Taxpayer Advocate Service (Form 911) can help. General information, not tax advice.