In the Business Partner Master Data window, on the Accounting tab, on the General subtab, you have clicked the Control Accounts browse button to open the Control Accounts - Accounts Receivable window.

In the Account Code column, you have done one of the following:

The List of G/L Accounts window has appeared.

In the List of G/L Accounts window, you have chosen the New button.

The Chart of Accounts Window has opened.

With the Assets drawer selected on the upper right side of the window, you have attempted to define a new account by entering information in the relevant fields.

You have chosen the Add button.

However, you have not selected the Control Account checkbox.