MB3 186b: Chalitza, Yibum, Divorcing, and Donating on Shabbos (339:4-5)

Yibum and chalitzah aren't done on Shabbos since they can lead to writing. Gittin on Shabbos.

Declaring an item hekdesh or hefker on Shabbos. Separating terumah/maaser/challah on Shabbos

Pledging money on Shabbos.