When you fill in the sales header on an order, invoice or credit memo for a customer whose credit limit has already been exceeded, the program issues a warning. It issues the same warning when you fill in a sales line or a general journal line. Posting the line results in the customer’s credit limit being exceeded.
Open the 
Sales Order
window.
Press F3 to create a new order.
On the menu bar, click Tools, Work Date, and enter a work date.
In the Sell-to Customer No. field on the order header, select a customer that has a credit limit, and then click OK.
Fill in the order line. For Help about a specific field, click the field and press F1.
The credit limit warning now appears.
Eliminating Credit Limit Warnings
Eliminating Overdue Balance Warnings