If you make a sale using invoice, you can later take partial payments which will be counted as installments.
First off, go to WP Admin Dashboard → WP ERP → Accounting → Expenses.
1. Open a Vendor Credit
2. Save the Credit for Approval
3. After the admin or accounts manager approves the invoice, you can make the sale and start receiving payments. At this moment the status of the invoice will be Awaiting Payment.
4. When a customer wants to make payment, you have to click on Receive Payment on the invoice.
5. A new payment will be opened. It will automatically fetch the amount of money you owe the vendor. You may change the value according to your need. Here in this payment, you can also see all the previous dues to this vendor if any.