I have pre-tax IRA and HSA deductions taken from my paycheck. When filling out line 4 of the Deductions and Adjustments Worksheet on form W-4 should I include these amounts, or are pre-tax deductions already accounted for before W-4 allowances are applied?
My understanding of this worksheet is that it is used to help you figure out what sort of deductions you will have on your tax return that are not already deducted from your W-2 income by your employer.
For example, if you contribute to an HSA on your own and claim the HSA deduction on Form 1040 line 25, you would want to include it here on this worksheet. However, if you are contributing to it through payroll deduction and your employer takes these amounts off of your income before it hits W-2 Box 1, you would not include it here. This line of the worksheet is basically for anything that you would deduct from your income on lines 23-35 of your Form 1040.
Instead of using the W-4 worksheets, you may want to try the IRS Withholding Calculator. This is a feature on the IRS website that tells you what to put on your W-4. It is more comprehensive than the standard worksheets and gives you better guidance on what to do.