How do I add notes to a payment?

If you have not yet posted/taken the payment click on 'View Transactions' on the RES or RESX item and then press the "+Add Transaction" button. As you are filling out the details, you will see that there is a field called "Additional Info" for you to add notes:

If you need to add notes to an existing payment you need to click on the drop-down arrow next to the payment type column as shown below:

It will appear in a pop-up box on screen, update your info and then click 'Update' to save.