When bookkeeping has fallen behind, the first step is usually a review of what records already exist — bank and credit card statements, receipts, invoices, and any prior reports — so a clear picture of the gap can be established before any correcting entries are made.
From there, the typical approach is to reconstruct transactions period by period, matching statements against the books and flagging anything that doesn’t reconcile. Categorization is checked against a standard chart of accounts, and open items are noted for follow-up.
Once the accounts are reconciled, the books can be brought current and a regular monthly rhythm put in place, so the same gap doesn’t reopen. The exact timeline and scope depend on how far behind the records are and how many accounts are involved.