Shaykh Fawzaan (0:25)
"Nothing should be
written on the Mushaf. However, you can write on a separate paper and attach it
to the cover of the Mushaf, that is alright. As for writing on or inside the
cover of the Mushaf then that is not appropriate."
Arabic Source:
Translated by Umm 'Abdir Rahmaan Tara Hashim 1437/2016