How to respond to IRS Letter 45C for Form SS-4

November 14, 2026 · 1 min read

The IRS uses Letter 45C when a Form SS-4 lacks information needed for processing. Review the request against the copy you submitted and follow the response instructions. The IRS may ask for a corrected or complete form and supporting documents.

What to check

A partial fax, unreadable form, or missing entry can produce this letter. Check the exact fields the IRS named, including continuation pages or supporting material if requested. Preserve the letter and submission record. If the letter is unclear about the status of your application, ask the IRS before starting a separate request for the same entity.

Example

An LLC's letter identifies line 8b, where the number of members belongs. The signer checks the ownership records, completes that item and returns the application and any requested material by the method the letter specifies.

Before you proceed

Confirm the letter number and date.
Compare the issue with the signed copy you submitted.
Save the corrected version and the response confirmation.

Does Letter 45C confirm that I have an EIN?

The letter can request information needed to process the application. Use a separate IRS confirmation or ask the IRS to verify whether an EIN has already been assigned.