Duplicates in QuickBooks Online usually happen for a few reasons. Bank feed rules might automatically categorize transactions you’ve already entered manually. Deposits can get recorded both as invoice payments and again from the bank feed. The same expense might get entered twice by mistake. And merchant processor payouts often overlap with individual sales records.

Bank rules are convenient but can cause problems. If you set up a rule to categorize Home Depot purchases as materials, then also enter those expenses manually, you’ll have two entries for the same purchase. Check your rules under Banking, then Rules, and make sure you’re not auto-accepting transactions you’re also entering by hand.

Invoice and deposit matching trips up a lot of business owners. When a customer pays an invoice, you mark the invoice as paid. That payment also shows up in your bank feed as a deposit. If you add the deposit as new income instead of matching it to the existing invoice payment, your revenue is overstated. Always match bank feed deposits to existing invoice payments rather than creating new income entries.

Merchant processor payouts create similar issues. Square, Stripe, or PayPal deposit one lump sum into your account, but you might have individual sales already recorded from the POS system or invoicing. The payout isn’t new income. It’s a transfer of money you already recorded as sales. Recording it as income again doubles your revenue.

Manual duplicate entries happen when someone enters a bill or expense, then enters the same thing later without realizing it already exists. This is common when multiple people have access to the books or when catch-up bookkeeping gets done in batches. Having one person responsible for full-service bookkeeping reduces this kind of overlap.

The best way to catch all of these is regular bank reconciliation. When your QuickBooks balance matches your bank statement to the penny, you know every transaction is accounted for once and only once. If the numbers don’t match, duplicates are often the reason. Reconcile monthly at minimum, weekly if you have high transaction volume.

Source document review catches what reconciliation might miss. Pull your vendor invoices, bank statements, and payment processor reports. Compare them to what’s in QuickBooks. If you have one invoice from a supplier but two expense entries, that’s a duplicate. If your Square payout report shows $3,200 but your income for that period is $6,400, you’ve probably recorded sales twice.

Running a Profit & Loss detail report and scanning for identical amounts on the same date can also reveal duplicates. Two $847.32 expenses on the same Tuesday to the same vendor is worth investigating.

If your books consistently have issues, don’t wait until tax season to fix them. Duplicates inflate expenses or overstate revenue, both of which create problems for business tax preparation. Monthly reconciliation and source document review are the most reliable ways to keep your QuickBooks data accurate.