There's some funny business afoot, thanks to the various "disaster relief", "COVID relief" and "inflation reduction" laws.
For context, this calculation is used to apply the Deason rule to work expenses when clergy have both a taxable salary and an excluded housing allowance. Self-employed clergy can deduct work-related expenses from their income on schedule C and from their income subject to SE tax on schedule SE. Clergy who are W-2 employees (which is most, really) can't deduct work-related expenses as itemized deductions using form 2016 because that was eliminated for 2018-2025, but they can still subtract work-related expenses from their income subject to SE tax on schedule SE.
And, when we are talking meals, we are mainly talking about meals taken when traveling away from home. Meals taken locally are usually disallowed because they are regular personal expenses and are never allowed, or they are "entertainment" which is disallowed by tax reform for 2018-2025 (see publication 463). Local meals are sometimes deductible if you are present and business is conducted. Then, remember that you can normally deduct 50% of your actual meal cost or 50% of the federal meal and incidentals rate for the place you are eating the meal.
Now, look at the very first paragraph of pub 517, it notes under "what's new" that "certain" meals may be deducted at 100%. To understand what that means, you need to know more about publication 463 and IRS notice 2021-63. Briefly, one of the disaster relief acts says that for 2021-2022, if you eat a work-related meal at a restaurant, you can deduct 100% of the cost instead of 50% of the cost. (Which also means that if you bought food at a grocery store and cooked it yourself, you can only deduct 50%, which seems a bit unfair.)
Then IRS notice 2021-63 says if you use the Federal MEI flat rate, you can assume the meal portion of the flat rate allowance was eaten at restaurants and deduct 100%. (You can't deduct the Incidentals portion of the flat rate.)
So bottom line, if you use the federal flat rate for your deductible meals, you can deduct 100% of the meal portion of the flat rate. If you want to use the actual expense method, you can deduct 100% for restaurant expenses and 50% for non-restaurant expenses. For 2022 only.
Look up the MEI rate here
https://www.gsa.gov/travel/plan-book/per-diem-rates/mie-breakdown
Pub 517
https://www.irs.gov/pub/irs-pdf/p517.pdf
Draft 2022 pub 463.
https://www.irs.gov/pub/irs-dft/p463--dft.pdf
Notice 2021-63
https://www.irs.gov/newsroom/irs-provides-guidance-on-per-diem-rates-and-the-temporary-100-percent-d...
