What Is a Letter of Explanation in Mortgage Underwriting?
An underwriter reviewing a mortgage file doesn’t just see numbers; they see gaps, deposits, and inconsistencies that a computer flags automatically but only a person can actually explain.
The short answer
A letter of explanation is a short, written statement from a borrower that clarifies an item in their mortgage file that an underwriter flagged as unusual or unclear, such as a large deposit, a credit report dispute, or a gap in employment. It’s a routine, common request rather than a sign of a serious problem, and it’s typically used to give context that documents alone can’t provide.
Common triggers for a request
Underwriting software and human reviewers both scan for patterns that look inconsistent with the rest of a file, and a letter is often the simplest way to resolve the question without requiring an entirely new set of documents:
- Large or unusual deposits. A deposit that doesn’t match the borrower’s regular income pattern often prompts a request to explain where it came from, since lenders want to rule out undisclosed debt or unverified funds.
- A gap in employment. As covered in more detail elsewhere, an employment gap frequently comes with a request for a written explanation alongside supporting documentation.
- Credit report issues. Late payments, collections, or a recent hard inquiry can prompt a request for context, especially if the issue seems out of step with the rest of the applicant’s credit history.
- A change of address or name. Sometimes a letter is requested simply to clarify a discrepancy between what’s on an application and what shows up in public records.
What a useful letter typically includes
A good letter of explanation tends to be brief, factual, and specific rather than lengthy or defensive. It generally states what happened, when it happened, and why it isn’t a sign of ongoing risk, often paired with supporting documents rather than standing alone. For a large deposit, that might mean a letter stating the source of the funds alongside a bank statement or gift documentation; for an employment gap, it might mean a brief account of the timeline paired with an offer letter from a new job.
Why underwriters ask instead of assuming
Underwriting guidelines generally require that anything unusual in a file be explained and resolved before a loan can be approved, in part because lenders are held to standards around documenting how a borrower’s income and debts were verified. A letter doesn’t override the underlying documentation requirements; it supplements them, filling in the “why” behind numbers or dates that would otherwise raise unanswered questions. This is part of why the request can come up even in an otherwise straightforward file — it’s less about suspicion and more about completing the record.
A practical habit
Borrowers who anticipate an unusual item in their file, such as a recent large transfer or an employment change, are generally better served by drafting a clear, factual account of it before being asked, since having the explanation ready alongside supporting paperwork can shorten the back-and-forth during underwriting. Because what triggers a request and how it’s evaluated varies by lender and loan program, the specific expectations are always worth confirming directly with the loan officer handling the file.