Please watch this video or follow the steps below:
1) When creating/editing an invoice, click Add Line and you can choose any option.
2) Name the item "Discount", "Waive", or "Write-off" (or anything else you like).
3) In the Price column, add the total amount of the discount/write-off (for example, $100).
4) IMPORTANT - Make the Quantity column -1 (must be a negative quantity).
What happens now?
PracticePanther will subtract money from the total in the invoice.
This negative amount is necessary for accurate Quickbooks accounting and proper sync purposes.