If you are entering a sales order and change the receipt date on the line and receive a message

The entered receipt date mm/dd/yyyy is not valid because it is not an open date in the customer calendar

Then you might want to check the receipt calendar assigned to the customer master. More than likely the date is closed for receiving goods on the date that was entered.

Here is a quick overview.

AX2012 R3 CU9

Cheers

Lachlan