Record the payment for the amount that actually arrived. Anything above the balance becomes a customer credit automatically.
To use it:
1.Open any open invoice for that customer.
2.A blue panel shows the credit available.
3.Press Apply. It settles as much of the invoice as the credit covers.
No money moves when you apply it — it already arrived.
Why it is not recorded as income
Until the credit is used or refunded, the money is still theirs. Booking it as revenue would report a sale that did not happen and hide a debt you do owe.