Offering discounts for early payment can be done by entering the amount of the discount using the small wheel with the "$" symbol that is located in the Fee Calculation Box:
A box will pop up and you can enter the amount and the expiry date of the discount. When printing the co-payment or gap account the discount text will appear and the amount due will update. See the image below for how it will appear on the invoice:
If you wish to edit the discount text that is displayed, simply go to your template editor in the CE Menu, under the "Settings" section:
Pre-Payment and Co-Payment templates each have a section that will automatically be added to printed invoices that have an active discount applied to them:
NOTE. When only taking a co-payment (ie not payment in full upfront) and charging the maximum gap allowable by a known gap fund if the patient is late paying and forfeits the discount the invoice will calculate based on an exceeded known-gap (ie the fund payment will only be up to 100% of the MBS) This is very much an edge case but should be considered when charging the maximum allowable gap.