When entering a payment or credit note against a charge, the date of the payment/credit note cannot be less than the date of the charge. This is because technically, the amount is an advance paid by the member, which would be adjusted against the charge on the date of the charge.
For these payments, enter these as advance payments (excess payment) in the system either as a Generic Advance or advance in the charges head. The system will automatically adjust the payment against the charge in ascending order of date of charge with the earliest unpaid charge being adjusted first.