Goods Received Date on the Invoice Header - How can we make it mandatory

We have a requirement where the "Goods Received" field should be entered with a date when Invoices are created Manually. When we click on "Show More", this date is visible and the user should be populating. Even though the field is shown to be mandatory, the user can create and save the transaction without adding in any date. How can we make it mandatory for user to enter the date?