Define the expected reporting set
Build an expected-properties table for the reporting period. Include a stable property identifier, reporting owner, source system, expected submission, and whether that property is included for the full period or under a documented exception.
Do not derive that list only from the files that arrive. If the collection process receives nine files, it cannot tell you whether ten were expected. The expected set needs its own source and an owner who can explain additions, disposals, and reporting exclusions.
Property names should be display labels. A building may have an old name in one export and a new name in another. Join records with a stable identifier and retain a reviewed alias mapping where needed. A model can suggest a possible match, but an uncertain match should remain unresolved until someone approves it.