From personal letters to business cards to emails, one comes across the Hebrew letters bet-heh or bet- samech-daled in the upper-right corner. They stand for “with God’s help” in Hebrew and Aramaic, respectively b’ezrat Hashem, or biseyata d’Shmaya.
Beginning any correspondence with a reminder that all we do is possible only with God’s help is certainly a good thing. But there is no mitzvah commanding us to write either b’h or bs’d. A quick survey of various rabbis’ letters reveals that while some did write it, others did not.
Rabbi Moshe Feinstein wondered why anyone would want to mention God at the beginning of a letter about mundane matters or even gossip. Some medieval sages began letters with an abbreviation of the declaration, “With the name of God we will do and succeed”. Writing this or other worthy initials at the top of the page is fine if it’s sincerely meant, but not as an empty piety.