Final answer:
To reconcile your bank records in QuickBooks when a check is lost in the mail and never cashed, you should void the check.
Step-by-step explanation:
In QuickBooks, when a check is lost in the mail and is never cashed, you should void the check to reconcile your bank records. This ensures that the amount of the check is not deducted from your bank account.
To void the check in QuickBooks, you need to go to the check register and locate the check in question. Then, you can select the check and choose the option to void it. This will update your bank records accordingly.