There are a couple of different file reviews - are you talking about decisioning or rate and terms? Also, if the bank is going to perform a fair lending review, are there internal guidelines of what to do in the event that the review uncovers any unfairness?
IMHO, a lot would be already determined by the controls in place, if there is any discretion to underwriting (centralized?), pricing, etc., if there is a 2nd review by someone competent (rather than a rubber stamp), if policy covers exceptions, and if the exceptions are recorded, analyzed, monitored and reported.
1 - Validate the self-assessment. If there is a consistent policy, no loan officer discretion for policy issues, and a robust second review, there should be no underwriting issues. If the bank goes by the rate/term sheets, with the only discretion being what is allowed by policy (e.g. auto withdrawals from XXX Bank's checking account get a 0.25% rate reduction), there should be no pricing issues.
2 - The bank could modify the review by identifying the declined loans that have a better (LTV/DTI/Credit score) than approved loans to ensure that the decisions were appropriate, and concentrating on that comparison. As long as there are no exceptions in the sample, call it a day.
3 - If resources are an issue, outsource the fair lending review.
The decision should be made by management, Audit Committee, etc., and documented.
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Integrity. With it, nothing else matters. Without it, nothing else matters.