If you need to keep a record of your customers and vendors' credits in the system you can do it by entering them in the Credit Memo module.
Subsequently, if you want to apply these credits to an Invoice, you can do it by following the next steps.
First, go to the AR Browser and filter by Customer.
Then select the invoice to which you want to apply the credit memo and choose the option to "Manage Payments".
If this Customer has credit memos, they will appear at the end of the window and you'll be able to apply them to the invoice.
Select the credit memo and click on "Save".
Subsequently, if you want to apply these credits to an Invoice, you can do it by following the next steps.
First, go to the AR Browser and filter by Customer.
Then select the invoice to which you want to apply the credit memo and choose the option to "Manage Payments".
If this Customer has credit memos, they will appear at the end of the window and you'll be able to apply them to the invoice.
Select the credit memo and click on "Save".