To void checks from prior months, enter a journal entry in the current month. The journal entry will debit cash and credit the same account from which the original check was issued.
If the check needs to be reissued, cut the check as you normally would from the same account. The credit made by the journal entry will absorb the new debit made by reissuing the check and cause the MTD change to be $0.
When completing the bank reconciliation, clear the journal entry against the original check.