To Unapply entries – go to the customer ledger entries (or vendor ledger entries)
I am going to unapply the invoice and payment below:
Look for Unapply Entries in the Ribbon
Select either the payment or the invoice line and select Unapply Entries
You will see all the transactions applied to the one transaction – there could be many lines here
Select Unapply
You will get this message – select Yes
You will get this message if successful
The entries are now open