Step 1: Click on Monthly >> Accounts from the left side menu of the screen
Step 2: Click on the Monthly Customer Account
Step 3: Click on Billing >> Billing Tab
Step 4: Choose the invoice and click on the option Reverse/ Write Off
Step 5: If you need to Reverse a invoice, select the Reverse option and click on Reverse
Step 6: If you need to Write Off a invoice, select the Write Off option and click on Reverse