What incident causes the Franks to go into hiding?

Although Mr. Frank has been preparing the annex as a hiding place, Margot's call up for the SS pushes the move into high gear. Mr. Frank isn't going to take a chance with his daughter.

On sunday,5 July,1942,Margot gets a call that threatened the family to leave Holland.Morover,as there was strict inspection of the Jewish areas for dragging them to concentration camp,which prompted Otto Frank to leave for hiding with his family on 8 July,1942.