problem wih entering a check

When you use Accounts Receivable, you need to choose a customer. If you are refunding the customer's A/R balance, choose the customer in the Purchased From or Pay to the Order Of field at the top of the screen. Otherwise, choose the customer in the Customer field in the Split table at the bottom of the screen. If you don't see a Customer field, Expense tracking by customer is turned off. To turn it on, you can go to Preferences and find it under Vendors & Purchases