Reversing a Customer Receipt and allocating a portion to another Customer

SOLVED

Hi I have a customer that has two separate accounts on SAGE50.  I do not receive Remittance Advices and normally the narrative on the Bank informs me which account lodgements should be allocated to.  In April I received a lodgement which for all intents looked like the full amount should do to Account 1.  It has come to light that the customer intended the lodgement to be divided between Acc1 and Acc2.  Since then, I have done the Bank Reconciliations for April onwards and our Accountant has closed off Apr-Jun.  What is the best way to correct this error.  It has been suggested that I do an invoice and credit this will show up on Statements and I suppose I can put a note in an accompanying email.  Another suggestion is do a receipt and refund this month - again the dating will be incorrect on Statement.  Is there anyway to correct this and keep the correct dates, or is that completely out of the question?  Thank you.