The short answer
Do not try to repair every month at once. Freeze avoidable changes, collect the source records, identify the oldest reliable balance and work forward in a controlled sequence. If a BAS is overdue or may be wrong, surface it early so the registered practitioner can confirm the correct next step.
A sensible catch-up sequence
- Assess.Confirm the entities, accounts, software, affected periods, lodged statements and known gaps.
- Protect the evidence.Keep statements, invoices, payroll records and prior lodgement material. Do not overwrite a questionable file without a recoverable copy.
- Set the starting point.Test opening balances and control accounts before reconciling forward.
- Resolve exceptions.List missing records, private-use items, duplicate entries and questions for the owner or tax agent.
- Validate and hand over.Define what “current” means, record the remaining issues and move into a repeatable monthly rhythm.
What to gather first
- Bank and credit-card statements for every affected period.
- Sales invoices, supplier bills, receipts and loan statements.
- Payroll, PAYG withholding and superannuation records where relevant.
- Copies of lodged BAS or IAS and any ATO correspondence.
- The last reliable reports, accountant adjustments and opening-balance evidence.
- A list of known missing records and the person responsible for finding them.
Keep ownership of the records
A bookkeeper can organise and work with records, but the business remains responsible for retaining the source records required by law. Use named access and secure invitations rather than shared passwords or public links.
When the backlog needs another adviser
Income-tax questions, legal disputes, insolvency concerns and work outside BAS-agent scope need the appropriate registered or licensed adviser. A good catch-up plan identifies those boundaries instead of burying them inside reconciliation work.