In MYOB Accounting Plus, you can track work on retainer in two ways. The first is to create a customer credit for the retainer amount and then apply the outstanding payment to invoices you record for the customers who retain you. The other is to create an order on which you can enter billing information when you're ready to record it as an invoice. Either method will work well, but they both affect your accounts in a different way. You may want to ask your accountant which method is best for you.