To void a payroll check, go to Banking → Account Register. Select the Account and the Period during which the check was printed. Locate the check and double-click on it to open it. Now click the Void button.
You will not be able to void a check that has been marked cleared in the register. If a check is marked cleared, the void option will be grayed out. You will need to 'unclear' the item first before it can be voided. When a payroll check is voided, the information will go back to the Process Payroll screen.
You should not attempt to void a check after any of the taxes have been paid for that payroll period.