Reconciliation ties each account's QuickBooks balance to its bank or credit-card statement until the difference is zero — the proof that capture and categorization were actually complete for the period. It happens monthly, once each statement closes.
In practice you open the reconcile tool, enter the statement's ending balance and date, and check off every transaction that cleared. What is left over is either genuinely outstanding — a check that has not cashed yet — or a sign that something was missed, duplicated, or miscategorized upstream. A zero difference is not busywork; it is the single strongest signal that a small-business file can be trusted, and it is why reconciliation anchors the monthly close. QuickBooks documents the exact steps for its reconcile workflow in its official help (Intuit QuickBooks support). Reconcile every month and drift never gets the chance to compound.
Outstanding versus missing
The difference between an outstanding item and a missing one is the whole skill of reconciliation. An outstanding item is real and will clear on a later statement — you leave it alone and it resolves itself. A missing or duplicated item is an error in the file, and the reconciliation is what surfaced it. If the account will not come to zero after you have accounted for genuine timing differences, stop and trace the discrepancy rather than forcing an adjustment; a forced reconciliation hides the very problem you were trying to find.