In 17hats you have a couple of options for recording discounts:
Add a discount to the entire invoice: this amount is subtracted from your income generated by the invoice when paid.
Add a line item for specific discounts: This will require you to set up a custom bookkeeping category.
 Adding a discount to the entire invoice
At the top of your invoice, you can add a discount that is either a fixed amount, or a percent of the total invoice.
Note: This amount will only be subtracted from income received on this invoice. You will not see it reported on the P&L.
 Adding a line item for specific discounts
If you'd like to list out what your discounts are for, you can do this by adding individual line items to your invoice. These will be (-) amounts, and require you to set up a custom income category in Bookkeeping.
Next, add the discount item to your invoice:
You will now see this discount applied to your total invoice:
When paid, your P&L now shows a report of what Sales Income was received, and what Discount ("Contra-Income") was received.
Keywords: Discount, Contra-Income, Coupons, Sales, Expense, Income, P&L, Profit & Loss Report