Moon POS allows you to add the discount before tax.

Below are the steps to follow : 

1. Open the Moon POS application on your device, or tap this link.

2. Go to POS > Menu.

3. Tap on the ‘Discount Icon‘ on the top bar and enable the ‘Discount Before Tax’ option to apply the discount prior to the tax.

                                                                                                                                           - Moon Invoice