Week one: produce the first report
Do not begin with a giant cleanup spreadsheet. Start with enough invoices to generate a starter report and reveal what is missing.
That report creates the motivation and structure for the rest of the cleanup.
Weeks two and three: critical systems first
Process fire, HVAC, roof, elevator, plumbing, and electrical documents before minor repair receipts.
Ask vendors for missing certificates or reports while the missing-record list is clear.
Week four: install the habit
The cleanup only sticks if new invoices enter the system as they arrive.
Forwarding or uploading invoices should become the maintenance history habit, not a quarterly archaeology project.