You can take partial or complete payment against each invoice either through invoice listing page or after opening an individual invoice. 

If you want to add a payment from invoice listing, simply click an invoice's Action button and click on Add Payment. 

You can also open an individual invoice and add payment from there. Click on Action button and select Add Payment.

A pop up screen will open. Here you can add amount, payment method, time and date of payment and additional notes. Once finished, hit Add button and the amount will be added against invoice.  

If invoice is paid already, a pop up will display an error message that this invoice has been paid already.

FAQs
Q. How can I restrict employees from repayment of an invoice?
A. To do so:

1. Head to Roles Permission under Employees in Settings.
2. Select Employee Role.
3. Click on Invoices section to expand section and view triggers.
4. Disable the trigger "Repayment of Invoice".
5. Click on Save Changes.

Now employees will be restricted from adding a repayment of an invoice.

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