The rules say a manager can remain as long as he has enrolled on the Pro Licence course.
But Southgate's sudden move from playing to coaching in the summer, when he replaced Steve McClaren mean he has not yet had a chance to study for the Uefa B and A badges, which he must have before he can apply for a Pro Licence.
He is in the process of acquiring his B badge, and will start studying for the A qualification in the new year with a view to taking the Pro Licence in the summer.
In its statement, the board said it had taken into account that he was until recently an international footballer, which had denied him the opportunity to take the necessary coaching courses.