In Haibooks, you can allocate a Credit Note to a bill.
How to Allocate a Credit Note ?
First, you must click on Purchases form the side bar menu and then Bills from the drop-down menu.
Select the credit note you wish to allocate.
Click on the button with three dots and then on Allocate Credit Note.
Enter the amount you want to allocate to the corresponding bill.
Click on Save when you are happy with the amounts allocated.