Scenario
I often see this request via support so thought I’d document it on my blog. The question varies however it usually goes something like this:
“I’ve accidentally applied an invoice to a Payment and now I need to unapply this however when I select the Payment in the “Transactions > Purchasing > Apply Payables Document” window the Invoice isn’t available to unapply? How can I unapply the invoice?”
The issue here is the “Apply Payables Document” window only shows OPEN documents and as the invoice has been fully applied its now in HISTORY. Therefore you can’t unapply it via this window.
Please note if both documents were in OPEN you could use the “Transactions > Purchasing > Apply Payables Documents” window to unapply it.
The solution in summary
Unfortunately there’s no easy way to unapply the invoice in this situation.
The fix I often suggest is to apply a dummy transaction to the payment so that it’s also transferred to HISTORY. You can then void the payment, which will unapply the Invoice.
Therefore, in summary, the steps would be:
- Post a dummy invoice (or debit note) for the amount remaining on the payment.
- Apply the dummy invoice to the payment which will send the payment to HISTORY.
- Void the payment via “Transactions > Purchasing > Void Historical Transactions”. This will unapply the Invoice.
- Void the dummy invoice via “Transactions > Purchasing > Void Open Transactions”
- Post the voided Payment back onto the system.
Detailed solution with an example
I’ve also described the scenario and solution in detail below.
Invoice INV123 has been accidentally applied to Payment 20069 when it should have been applied to Payment 20070. As a consequence Invoice INV123 is in HISTORY but Payment 20069 is still in OPEN meaning the invoice can’t be easily unapplied

To fix this we first post a dummy invoice for $80.00 (the remaining amount of payment 20069):

Next we apply this to the Payment via “Transactions > Purchasing > Apply Payables Documents”:

Now the Payment and invoices all show in History:

Next we void the payment via “Transactions > Purchasing > Void Historical Transactions”

Invoice INV123 is now showing as unapplied (as is the dummy invoice):

We now void the dummy invoice via “Transactions > Purchasing > Void Open Transactions”

And finally post the payment back onto the system

Once this has been done you can go ahead and apply invoice INV123 to the correct payment.
Conclusion
Although there are many steps to unapply the invoice using this process, it does provide a way of unapplying the invoice.
I hope this helps someone in the future.
Thanks for reading!