You should keep the number of edits to the approved invoices to the minimum possible. This is because once a purchase entry is approved, the accounting entries for these are created in the system. Hence when it is edited, the corresponding entries has to be passed into the accounting system and the vendor GL will reflect these.
However, in the event that the purchase has to be amended, the invoice details such as invoice number, invoice date, rate, and other related fields can now be edited directly in the existing bill and saved successfully without the need to reject and recreate the bill.
If there are quantity changes, then the bill has to be rejected and the GRN has to be deleted. You can create a new GRN using the cancelled GRN so that you do not have to manually create it again.
Refer the below video for the details.