How to size a sample for loan origination file audits

Sponsors often ask for “enough files to be credible” without wanting a statistical lecture. For a financial audit of loan origination applications, credibility comes from a clear frame and honest limits, not from a mystical percentage.

Start with the decision

If the credit committee needs comfort on a festive campaign, draw only from that campaign code. If the question is override hygiene across the whole personal-loan book, stratify by facility size so large exceptions are not drowned by small ticket volume.

Volume bands we see in practice

For books writing fewer than 200 facilities a month, reading 40–60 files often surfaces repeating document gaps. For higher-volume consumer books, 80–120 files across two or three strata is a common starting point for a full origination file audit. Sampling reviews sit lower when the checklist is narrow.

What not to do

Do not let branches pick the “good” files. Do not top up the sample mid-fieldwork with replacements that erase early exceptions. If access fails on a drawn file, record the access failure as a finding of its own.

Closing the loop

Publish the draw rules in the engagement letter. When the memorandum lands, the committee should be able to see why these loan origination applications—and not others—were opened.