RE: How to manually tag a Purchase Invoice and Sales Invoice when paid from the Posted Invoices?
I'm going to give you the steps
1. go to Vendor card then vendor ledger entries (or go to vendor ledger entries and filter for one vendor at a time)
2. position your cursor on the payment you want to apply
3. choose Process>>Apply Entries
4. For each invoice to be applied to the payment, position your cursor on the line
5. Choose Process>>Set Applies to ID
6. Once you've selected all the invoices for that payment, Choose Process>>Post Application
7. Repeat steps 1-6 for all payments for all vendors.