Great news, @Vitan!

You can turn on the Discount feature to easily add and track discounts in your invoices.

Here's how to turn it on:

1. Go to the Gear icon.
2. Under Your Company, choose Accounts and Settings.
3. Select Sales.
4. Click Sales form content.
5. Put a check for the Discount option to turn it on.
6. Click on Save and then Done.

Once done, you can add a discount in the Discount field of your invoice.

Please see screenshot for your visual reference.

Also, you have the option to add a discount as an item of your inventory. Please read the article to learn more about this: Discount as Line Item on Invoices and Sales Receipts.

Feel free to leave a comment below if you have any other concerns.