If the borrower doesn't respond within the stated timeframe, you can consider it not accepted:
3. Action taken—application approved but not accepted. A financial institution reports application approved but not accepted if the financial institution made a credit decision approving the application before closing or account opening, subject solely to outstanding conditions that are customary commitment or closing conditions, but the applicant or the party that initially received the application fails to respond to the financial institution's approval within the specified time, or the closed-end mortgage loan was not otherwise consummated or the account was not otherwise opened. See comment 4(a)(8)(i)-13.
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All opinions are my own, not my employer's