Hello Rose,
In addition to steps suggested by Connie,
If the checks are already recorded in the system and if you need to void the check, Please follow the steps below.
1) Payment management / Liquidity management work center
2) Payment monitor view
3) Search for the outgoing checks which you need to void. (Check should be in status "In transfer")
4) Click on Actions for checks
5) Enter Voiding date and Void Reason
6) Click Ok
You could find information on how to void the check (Steps suggested by Connie) in the help center document : "Check Lots and Check Numbers for Outgoing Checks" under the section : "Skip Next Check Number"
I hope this helps.
Cheers,
Harshal