Problem
Customer 1 has a payment credit that was added by mistake and instead needs to be moved to customer 2.
Solution
Create an invoice for customer 1.
On the invoice, click Add an adjustment invoice.
On the adjustment invoice, create a temporary task for the credit amount.
Go back to the invoice you created in step 1 and click Collect and apply payment.
Select the credit that was incorrectly added and apply it to the adjustment invoice created in step 2.
Go back to the adjustment invoice and add a negative payment for the credit amount. You should now have one positive payment and one negative payment on the adjustment invoice.
Delete the temporary task you created in step 3. This removes the credit from customer 1.
Go to customer profile for customer 2 and add a payment for the correct amount.
If the payment is by credit card, click the down arrow on the Charge option and select Save without charging.
If the payment is by cash or check, click Save.
Note: This prevents you from double charging the customer.