Letter 418C, Amended/Original Return Unavailable; Copy Requested, tells you the IRS cannot locate a return it needs to finish working your account. Usually that is an amended return, or an original return the IRS has a record of but cannot pull from storage. Under IRM 21.6.7, the IRS sends this letter only after it has tried to get the return from its own files and failed.
What the IRS Is Asking For
If you filed an amended or corrected return, send a complete, newly signed copy. A photocopy of your old signature is not enough. Include every schedule and form that went with the original. If you did not file an amended or corrected return, say so in writing so the IRS can correct your account.
The Timing
The IRS generally holds the case for 45 days waiting for your reply, 70 days for qualifying overseas taxpayers. If you do not answer, the IRS moves forward under its general claims procedures, which usually means your claim or adjustment is not allowed. If you were expecting a refund from the amended return, silence can cost you the refund.
Practical Points
Send the copy to the address on the letter, include the tear-off stub or a copy of the letter, and use certified mail. Keep a complete copy of what you send. If the return claimed a refund and the refund statute is close to expiring, write that clearly on your cover letter. Proof of when you originally filed matters in that situation, so include it if you have it.
If you received Letter 418C and cannot find your copy of the return, call us at (813) 229-7100. We can pull transcripts and reconstruct what was filed.