Start by gathering every source document you can find. Bank statements, credit card statements, invoices, receipts, loan documents, payroll records. You can’t fix what you can’t verify. If you’re missing documentation, request copies from your bank and credit card companies. Most provide at least two years of statements online.

Bank reconciliation comes first. Match every transaction in your accounting software to your bank statements, month by month. Start from the last month you know was reconciled correctly and work forward. If you’ve never reconciled, start from when you opened the books. Every discrepancy matters. A $50 difference usually means a transaction is missing, duplicated, or coded to the wrong account.

Once banks are reconciled, fix the categorization. Pull a transaction list and review how expenses are coded. Office supplies showing up as cost of goods sold, personal expenses mixed with business costs, vendor payments sitting in random expense accounts. Fix these one at a time. If you don’t know what a transaction is, look at the vendor name and amount, then verify with your bank statement or receipt.

Look for duplicates. Manual data entry almost always creates duplicate transactions. Bank feeds combined with manual entries cause the same problem. Search for transactions with identical amounts and dates. If you find two entries for the same purchase, delete one.

Review accounts receivable and accounts payable. Check open invoices against what you’ve actually received and paid. Old invoices that were paid but never marked closed make your receivables look inflated. Bills that were paid but never entered make your bank balance not match your books.

Fix the balance sheet. Opening balances, equity accounts, and loan balances should match external statements. If your loan balance in the software doesn’t match your most recent loan statement, something is wrong. Retained earnings should tie out from prior years.

The time this takes depends on how long the books have been neglected and transaction volume. A service business with 50 transactions a month that’s six months behind might take a weekend. A retail business with 500 transactions a month that’s two years behind could take weeks.

If you’re more than a year behind, have high transaction volume, or need accurate financials for a deadline like a loan application or investor meeting, consider bringing in help. A bookkeeping cleanup service is built for exactly this situation. They’ve seen every type of mess and know the fastest path to accurate books.

After the cleanup, the goal is to never need one again. Monthly reconciliation and review keeps books clean. A full charge bookkeeping service handles this ongoing so you’re not back in the same situation next year.