If you do not know beforehand if a specific invoicing address will be used for every invoice to a customer, do not fill in the Bill-to Customer No. field on the customer card. Instead, enter the bill-to customer number after you have set up a sales header (quote, order or invoice header).
Open the Sales Quote window.
Press F3, and then press Enter to create a new quote and give it a number.
In the Sell-to Customer No. field, select the customer you are going to sell something to, and then click OK.
Click the Invoicing tab.
In the Bill-to Customer No. field, select the customer who is going to pay for the purchase. Click OK, and then press Enter.
Now you have added a bill-to customer to the sales quote.