Do you tip Mormon missionary for service work?

No. Mormons missionaries are full-time volunteers who are not paid, are not given a living stipend, but pay their own way entirely. In fact, Mormons consider it somewhat of a conflict of interest to have any paid clergy. As such, neither the missionaries nor the local Bishop nor anyone in the 14M-member hierarchy receives any money for what they do.

In addition, Mormon missionaries are typically not allowed to accept cash gifts, so even if you tried to tip them they wouldn't accept. They can, however, accept gifts of food. If you feel you have to tip them, provide lunch or invite them for dinner.