Automatically use unallocated cash on invoice creation

Hi,

We have international customers who pay yearly for our services. Due to bank transfer fees they sometimes overpay to ensure the full amount reaches us, this is then deducted from the following year's invoice. I have added the overpayment as a transaction to the Trade Debtors account, which has added it to the customer's Unallocated Cash.

The problem is, how do I know it's there? The only indication I can see is by scrolling miles down the page past years of invoices to see Unallocated Cash on their statement. It is very easy to miss the unallocated cash when sending out the following year's invoice. Especially since the invoice is recurring.

When an invoice is created and there is unallocated cash in a customer account, the unallocated cash should be automatically paid to the new invoice, or at least the option to do so should be presented.