What Letter 2645C is
The first interim letter Accounts Management sends when it cannot answer within 30 days of the earliest IRS received date. The manual says "An interim letter is required to be sent within 30 days of the received date if a final response cannot be issued," and every interim letter must state when to expect final resolution (IRM 21.3.3.4.2.2(1)-(2), June 2, 2023). Since January 2018, interim letters generated through CII and AMS systemically promise 60 days (IRM 21.3.3.4.2.1(3), Nov. 22, 2022). It says nothing about the merits of your request.
The deadline
No action required. Expect the final reply by the date stated, normally 60 days from the letter.
What to do
File it with the letter it acknowledges. If the promised date passes with no reply, the manual requires a second interim, Letter 2644C, that "must include the specific reason for the delay" (IRM 21.3.3.4.2.2(4)). Once an interim is out, a closing letter must follow unless the closing action generates a notice (IRM 21.3.3.4.2.2(6)); a CP 210 or CP 220 that answers everything can be that closing (IRM 21.3.3.3.4(4), Dec. 19, 2023).
What the letter is actually telling you
The IRS's own description of Letter 2645C is a sentence long: it received your correspondence and needs more time to work it, and no action is required. The letter is generated by the Accounts Management function, which handles taxpayer correspondence, penalty abatement requests, amended returns and claims, when a case has sat for 30 days without a final answer. It will tell you roughly when to expect a reply, typically 60 days from its date, and it says nothing about what the reply will be. A 2645C after a reasonable-cause request means the request is in a queue and has not been read; it does not mean it is being taken seriously, and it does not mean it is in trouble.
Two practical points follow. The date it promises is a processing commitment, not a legal deadline, and the IRS misses it often enough that there is a second letter for the purpose. And the 2645C is the proof that your correspondence was received and when, which matters if a notice later says you never replied to something.
If you did not write, and when to escalate
Match the 2645C to the letter it acknowledges by the received date it quotes. If you cannot find anything you sent, call the number on the letter: a 2645C acknowledging correspondence you did not send can mean a return or a change request was filed under your EIN by someone else, which is the business identity theft pattern the identity theft guide covers. If you did write, file the 2645C with your copy and the certified-mail receipt and wait for the promised date. When that date passes, the next letter should be a 2644C with a stated reason; if neither a reply nor a 2644C arrives within two or three weeks of the promised date, that delay is one of the Taxpayer Advocate Service's case criteria (no response by the date the IRS promised), and a Form 911 is a reasonable next step. The correspondence guide follows a letter through the campus, and the calling guide covers how to get a status on an open case.
Questions about Letter 2645C
Who receives Letter 2645C?
Payer. The first interim letter Accounts Management sends when it cannot answer within 30 days of the earliest IRS received date.
What is the deadline on Letter 2645C?
No action required. Expect the final reply by the date stated, normally 60 days from the letter.
What should I do when Letter 2645C arrives?
File it with the letter it acknowledges. If the promised date passes with no reply, the manual requires a second interim, Letter 2644C, that "must include the specific reason for the delay" (IRM 21.3.3.4.2.2(4)). Once an interim is out, a closing letter must follow unless the closing action generates a notice (IRM 21.3.3.4.2.2(6)); a CP 210 or CP 220 that answers everything can be that closing (IRM 21.3.3.3.4(4), Dec. 19, 2023).
Is Letter 2645C about my own income tax?
No. This decoder covers information reporting and withholding: the notices a payer, filer or payee sees because of Forms 1099, W-2, 945 and the TINs on them. Individual income-tax notices follow a different track.
Have a different notice? The IRS notice decoder lists all 77 in the order they tend to arrive.