while in the service, or while away from their tax home (traveling around the mission).

When dealing with Meals and Entertainment within the parameters of a mission, it can get somewhat tricky. The law itself is pretty straightforward in that you can deduct the cost of meals while traveling away from home. The tricky part is the definition of “home.” Basically (and I am simplifying this significantly), your tax home is where you have been or will be for longer than one year within any given fiscal year (see publication 526 for more detail, specifically pg 6, which succinctly describes this, although does not provide any of the code citations).

So for instance, if the mission is only 11 months long, I would tell you that you can deduct the cost of your meals all day long, every day. However, if you are gone for longer than 12 months, this can get somewhat trickier and especially if the 12 months straddles two calendar years. It gets even trickier when looking at it from the standpoint that your initial mission may have only been contemplated to be 11 months, but was then extended for a longer period to 18 months.

Note also, that lodging is not deductible for the same reason unless it is paid directly to the Church with no ability to specify that it go directly towards rent. Rent paid for a greater than 12 month period is typically not deductible as a charitable expense when paid directly to the lessor.

Hope that helps.