The bank is right. Banks don’t make math errors on your balance. When the numbers don’t match, the problem is in QuickBooks. Your job is figuring out where.

Start with reconciliation. QuickBooks has a reconciliation function that compares your records against your bank statement line by line. If you haven’t been reconciling monthly, that’s the first problem. Run a reconciliation for each month you’ve missed, starting with the oldest. The reconciliation process forces you to match every transaction and reveals exactly where the discrepancy lives.

Look for unrecorded transactions. Bank fees, interest charges, automatic payments, and small transactions are easy to miss. If you’re not using bank feeds or you haven’t accepted all the downloaded transactions, some items are sitting in limbo rather than hitting your register. Check for transactions the bank shows that QuickBooks doesn’t.

Check for duplicates. If you manually entered a transaction and then the bank feed imported it again, the same item counts twice. This inflates or deflates your balance depending on whether it’s income or expense. Search for round-number amounts or vendors you pay regularly to spot duplicates.

Verify your starting balance. If the opening balance in QuickBooks was wrong when you set up the account, every month since then has been off by that amount. Compare your first bank statement after setup to the QuickBooks opening balance. If they don’t match, you’ve found the root cause.

Watch for timing differences. Your QuickBooks balance might include transactions you’ve entered but the bank hasn’t processed yet. Checks written but not cashed, transfers initiated but not completed, pending deposits. These aren’t errors, just timing. A proper reconciliation accounts for them as outstanding items.

Review deleted or voided transactions. QuickBooks lets you delete or void transactions, which changes your balance. If someone deleted something they shouldn’t have, the record is gone from your register but the bank still shows it. Run an audit log to see what’s been deleted recently.

Check for transactions in the wrong account. If you have multiple bank accounts in QuickBooks and accidentally recorded a transaction to the wrong one, both accounts will be off. One too high, one too low.

Once you find the discrepancy, fix it and reconcile. When your reconciliation shows a zero difference, your books match the bank. Going forward, reconcile monthly so discrepancies get caught while they’re still easy to trace. The longer you wait, the harder it gets to find where things went wrong.

If you’ve tried everything and still can’t find the problem, the books may need a deeper cleanup. Errors compound over time, and a discrepancy that started eighteen months ago can be buried under hundreds of transactions. A bookkeeper experienced in QuickBooks cleanup can usually find issues faster than someone unfamiliar with where problems typically hide.