Start with the evidence
Name the expected sources and who provides each one. Distinguish a source that has arrived from one that has been checked for completeness and the correct period.
Work through the example
Three of four expected sources are present, but the supplier receipt set is missing. Recording that gap prevents the review from appearing complete simply because the available files have all been opened.
Make the next step clear
Track the missing source and continue independent checks that do not depend on it. Keep the limitation visible in the final handoff rather than assuming silence means there were no documents.
Keep the source context
Keep the review period, source set and unresolved questions explicit. A checklist records work performed; it does not by itself establish that financial statements are complete or compliant. Use the appropriate reviewer for decisions about accounting treatment.