Per Diem
 

Does anyone know of Per Diem is taxed? With my last employers per diem was withheld at normal income tax rates.

Only if a day trip. All other per diem is left untaxed.

just to clarify, only if you have a single day trip?

Correct, two day trips and longer are non-taxable per-diem.

To put it another way, overnight per diem isn't taxed.

Now there is probably a slight difference as an UNSCHEDULED delay that doesn't go past 4AM IIRC is considered a second day for pay but it probably is for the IRS.

And BTW, a scheduled 1AM or later arrival is two days both ways.

Of course, that's not often so not a big concern probably.

A more simple way:

If you go to hotel for a legal rest period, no tax for entire trip/pairing.

If you never go to hotel, or that hotel is short and not FAA rest (nap or long day sit), taxes apply.