Hello Robin,

Under Payments | Check Reconciliation, highlight the check you want to reverse and use the right mouse button and select Reverse. The check will be reversed (with the appropriate g/l entries), but the invoice will remain outstanding (unpaid). You will need to post an adjustment if you want to back out the invoice too.

We recommend removing the ability to Void checks by setting the appropriate option in the Company Profile. Check "voiding" is there for historical and compatibility reasons.