It is a good idea for tenants and owners to keep a rental file. This should contain records of all leases, condition reports, letters, requests for repairs, notices to vacate/terminate, receipts and invoices.
The owner must also keep a rental ledger. See example rental ledger (XLSX, 12.6 KB)
Both tenant and owner should make sure that all important requests and notifications are made in writing and are signed and dated. These documents are very important in case any misunderstandings or disputes arise.