I want to have the maximum-possible US Federal Income Tax withholding made from my paycheck
By "maximum", I mean I want ALL of the remainder (after all other deductions) of my paycheck withheld, so that I have $0 net pay (after all deductions, including the Federal Income Tax deduction that I want to max out).
How do I instruct this on my 2020 W4?
(see accepted Answer for why this strikeout below, didn't actually result in $0 net pay prior to 2020)
This appears to be how to do it prior to 2020:
If you want to have the maximum amount of taxes taken out of your paycheck, then you need to claim zero allowances on line 5 of your W-4.
But in 2020, that won't work anymore since there is no more line 5 on 2020 W4 (for allowances):
3.What happened to withholding allowances?
Allowances are no longer used for the redesigned Form W-4. This change is meant to increase transparency, simplicity, and accuracy of the form. In the past, the value of a withholding allowance was tied to the amount of the personal exemption. Due to changes in law, currently you cannot claim personal exemptions or dependency exemptions.
So how can I do it with 2020 W4?
My best guess is to designate/enter an amount on 2020 W4 line 4(c) [for "Extra withholding"] that I know will be greater than [or equal to] my net pay per paycheck (the net pay I would get by default if I don't submit a W4) - would that indeed be how to do it? Or please let me know if there is a correct/different way (or if it somehow depends on my given employer).
Reason for wanting $0 net pay [at year-end]:
To benefit from the opportunity cost of deferring more income tax payment to the end of the year.
Increase withholding at year end: Even though additional tax is withheld at year end, the tax is deemed to be spread evenly throughout the tax year with an equal amount paid on each installment due date. This creates an opportunity for taxpayers who either find themselves underpaid or wish to defer the payment of tax to avoid the underpayment penalty by increasing withholding at year end (for example, 100% withholding on a year-end bonus)