Since I was bored I decided to do some number crunching, so here you go. These hours are from 40 weeks of retro due that I painstakingly added up. These numbers do not represent production bonus as the memo stated hours worked, holiday, vacations, will be paid
Regular hours (holiday included)1600 x .70 = 1120.00
Overtime hours 562.35 X 1.05 = 563.09
Double time 26.55 X 1.40 = 37.17
Giving a total of 1720.26 due in retro pay
Now I went back and tried to find a check that would accurately represent my particular tax bracket based on a closely matched check. The check in comparison is a 1796.90 as that's the lowest check I've made all year.
Deductions are as follows
FICA 111.41
FICA MEDICARE 26.05
FED TAX 183.43
STATE TAX 85.51
ROTH at 20% 359.38
UNION DUES 20.25
For a grand total of 786.03 in deductions.
1796.90 - 786.03 = 1010.87
So my Gross Retro pay is 1720.26 - X = 1018.00 (what was deposited in my bank today) insert 786.03 in deductions and it's pretty much a match.
All that to say, yes, 401k is deducted from your retro and the tax rate is your regular tax rate.