When a customer pays an overdue invoice by check, the clock starts on the day the check is written. Most banks follow the Uniform Commercial Code (UCC), which lets them refuse payment on checks older than six months, though some will still honor them at their discretion. A check dated more than 90 days ago is worth a call to your bank before deposit to confirm it will clear. Depositing a stale check that comes back unpaid means a returned-check fee and further delay.

Stale checks create an AR problem because they sit between "paid" and "actually received funds." Some businesses mark an invoice as paid when the check arrives, only to discover weeks later that it bounced or was refused. Best practice is to mark the invoice pending until the check clears. For checks older than 30 days, contact the customer to confirm the funds are still available before depositing, especially if the customer's financial situation may have changed.

In a collections context, a customer who sent a check six weeks ago that you never deposited has not legally paid the debt. You still have a valid claim. If the check is now stale, request a new check or an electronic payment. Don't accept a stop-payment promise without replacement payment in hand. Some customers use the stale-check situation to dispute the underlying invoice.