Choose "Leases" from the List menu on the left. 

You will find the lease page with grids of information about all leases. 

Just click on the lease to apply discount or waive off the late-fee.

In the lease page, you can see the button called More at the top right of your screen. Just tap on it and again tap on Apply Discount.

There appears a pop up window, Here you will have the privilege to give discount for the late-fee and waive off the late-fee. The below upcoming screenshot will give you the clear idea on this.

Enter in the discount amount in the Late-fee Discount text-box. Once entered you will see the variation in the below billing summary.

To waive off, Just check-in the box.

Also, In the transaction table you will see the discounted amount in the ''Credit / Payment'' column.