Pre-Tax vs. After-Tax Deductions: What Comes Out of Your Paycheck First
The order things come out of your paycheck changes how much tax you pay. A $100 deduction might cost you $100, or it might cost you $70. It depends on whether it's taken before or after taxes.
Pre-tax deductions
A pre-tax deduction comes out of your pay before certain taxes are figured. You pay less tax because the taxed amount is smaller.
But "pre-tax" doesn't always mean pre-every-tax.
| Deduction | Lowers federal income tax? | Lowers Social Security and Medicare? |
|---|---|---|
| Health, dental, vision premiums (cafeteria plan) | Yes | Yes, usually |
| Health savings account (HSA) through payroll | Yes | Yes |
| Flexible spending account (FSA) | Yes | Yes |
| Traditional 401(k) or 403(b) | Yes | No |
That last row surprises people: a traditional 401(k) contribution lowers your income tax, but you still pay 7.65% Social Security and Medicare on it.
State income tax usually follows the federal treatment, with exceptions. For example, Pennsylvania and Massachusetts tax 401(k) contributions at the state level.
After-tax deductions
An after-tax deduction comes out after taxes are figured, so it doesn't lower this year's tax:
- Roth 401(k) contributions
- Some life and disability insurance
- Union dues
- Wage garnishments
- Charitable giving through payroll
Roth vs. traditional, in one sentence
Traditional contributions lower your taxes now and you pay tax when you withdraw in retirement. Roth contributions don't lower your taxes now, but qualified withdrawals in retirement are tax-free. Which is better depends on whether you expect your tax rate to be higher now or later.
What a pre-tax deduction really costs
If you're in the 12% federal bracket and contribute $100 per paycheck to a traditional 401(k):
- Your federal income tax drops by about $12.
- Your Social Security and Medicare don't change.
- Your take-home pay drops by about $88, not $100 (less if your state also lowers its tax).
That's why a retirement contribution "costs" less than it looks.
Why this matters for planning
When you change benefits at open enrollment, or start or change a retirement contribution, your take-home pay changes by less than the deduction itself. To know the real effect, the taxes have to be refigured on the new, smaller amount.
IncomeSync handles deductions the way payroll does: health premiums, pre-tax and Roth retirement, and other deductions each come out at the right step, so your projected take-home pay matches your stub.
For planning, not tax advice.