A voided check is a check written or partially written but then canceled or deleted by the maker of the check.
The notation of "void" is used because checks are prenumbered for control purposes and every check needs to be accounted for.
Voided checks may require some adjustments when reconciling the bank statement. For example, if a check is written in December but is voided in January, the Cash account in the company's general ledger will need to be increased when the check is voided. (Another account will need to be credited because of double entry bookkeeping.)