When you are invoicing a client for a high amount, the client might want to pay off that invoice in multiple terms.
If you allow this, you can go into the invoice to do this. When you go to the top right corner of the invoice, you can change the amount to pay to whatever the client is paying at that moment. After that, you choose the payment method. Once you've done this, you will see the amount that is still left to pay is the total amount minus the payment the client has just made.You can continue doing this as many times as you wish until the amount to pay is zero and the invoice will be automatically switched to paid.