Void Selected Payments
This is the option to use when a check has been written incorrectly.  Voiding a check makes the necessary changes in the system but will not relieve the check number to be used again.

Void Unused Payments
This is the option when you have check stock that has not been used and will not be used.  Voiding these numbers in the system as unused tells the system to never allow these numbers to be recorded.

Purge Voided Payments
This is the option when a check has been recorded in the system but for some reason is incorrect or did not print on the physical check.  When you purge a payment it relieves that check number in the system to allow it to be used again.