From time to time, you may receive a payment, and not know which customer to allocate it to. First, set up a debtor card file (card code UNK.DEBTOR, or similar) to allocate these payments to until you can locate the correct customer.
Now add the payment against the unknown debtor's account via Debtors – this account will now show a credit balance.
Once you establish the correct customer, use the debtor adjustment functionality to move the balance from the unknown debtor account to the correct debtor account.
1.From the unknown account:
Add a debtor's adjustment up, tax code X, GL Account 4-XXXX debtor/creditor adjustments. This will produce an outstanding value. You will then need to allocate the credit to the outstanding invoice.
2.From the correct debtor account:
Add a debtor's adjustment down, tax code X, GL Account 4-XXXX debtor/creditor adjustments. This will produce a credit. You will then need to allocate the credit to the outstanding invoice.
Further information:
Debtors Adjustments Up and Down