Sheikh `Abd al-Rahmân al-`Ajlân, lecturer at the Grand Mosque in Mecca
It is preferred to recite “Bismillâh” before reciting each chapter of the Qur’ân, except for Sûrah al-Tawbah in which it does not appear. However, it is not obligatory to do so.
There is a disagreement among the scholars whether or not the statement “Bismillâh” is a verse of each chapter of the Qur’ân (except for Sûrah al-Tawbah), a verse of Sûrah al-Fâtihah only, or an independent verse on its own.
However, there is agreement that it is part of a verse of Sûrah al-Naml.
And Allah knows best.
Source: Islam Today