You can write-off all or part of an invoice by creating a "Write-Off" type billing item. If you create a write-off that reduces the invoice balance to zero, the status of the invoice is automatically set to “Write-Off."

1. Hover over the Billing module and select Billing Items.
2. Click the Add button. 

3. Select the Client.
4. Select Write-Off as the Type.

5. Once you select the Type you will be able to select the invoice(s) you wish to write-off. Select the Invoice(s). 
6. Enter the amount you wish to write-off in the Write-Off Amount field. 
7. (Optional) Enter a description in the Description field.
8. Click the Save button.