The Ruling on Writing Bismillah on invitation Cards
Writing Bismillah on cards and other messages is allowed, based upon the narration from the Prophet in which he said: Any important matter which does not start with Bismillah is a matter which is cut of (from every good thing). ý and because he used to begin his letters with the Tasmiyyah. It is not permissible for one who receives a card or letter in which Allaahs Name, or a Quranic Verse is mentioned to throw it in the rubbish or refuse, or to put it in an undesirable place. Likewise, it is not permissible to abuse newspapers and other such things, or throw them in the rubbish, nor to use them as eating mats for food, nor as wrappers for things due to the fact that they contain mention of Allaahs Name, the Almighty, the All-Powerful and because doing that involves sin. As for the writer, there is no sin upon him. May Allaah grant the Muslims success in attaining all goodness.
Shaykh `Abdul-`Azeez Bin Baz
Fatawa Islamiyah Vol. 5 Page 308