Question:

Is one required to stand during the recitation of Kaddish?

Answer:

The Shulchan Aruch1)Orach Chaim 56:1 makes no mention of standing during Kaddish. The Rema2)Orach Chaim 56:1 writes that one should stand at the time of answering to Kaddish. The Mishnah Brurah3)56:8 writes that there is no full fledged obligation to stand for Kaddish though one certainly may if they want to. He says that you should stand for a Kaddish that is said at a time when you are already standing (like after Hallel). He adds that according to the Magen Avraham and others it is praiseworthy to stand for all kaddeishim like the opinion of the Rema. There also seems to be a particular importance on a kabbalistic level to standing for the kaddeishim which are said directly prior to or directly after parts of the service where we must stand (i.e the Kaddish before the Amidah and the Kaddish after putting the Sefer Torah away4)Shar Hakavanos, end of the drush about Kaddish and Minhagei HaMaharil brought in Mishnah Brurah 95:3). The Sephardic custom follows the apparent approach of the Shulchan Aruch that one is not obligated to stand for Kaddish. Ashkenazic custom follows the approach that it is either praiseworthy or obligatory.

References   [ + ]

1, 2. Orach Chaim 56:1
3. 56:8
4. Shar Hakavanos, end of the drush about Kaddish and Minhagei HaMaharil brought in Mishnah Brurah 95:3