How to handle the GST invoice with discount on invoice value

Hi,

We are receiving few GST invoices having discount on invoice value. Kindly guide me on how to handle.

Item A price - 500

Igst 12% - 60

Item B price - 500

Igst 12% - 60

Invoice amount - 1120

Discount value - 50

Need to pay only 1070

Is there any option to do the purchase order, receipt and invoice properly?

Shanthi