What are post-tax deductions?+
Amounts taken from your pay after taxes have been calculated and withheld. They reduce the cash you receive but not your taxable income. Roth 401(k) contributions, wage garnishments, union dues, most disability premiums and charitable payroll giving are typical examples.
What is the difference between pre-tax and post-tax deductions?+
Pre-tax deductions come out before tax is calculated, so they lower your taxable income and your tax bill. Post-tax deductions come out afterwards and have no effect on tax. A $200 pre-tax deduction might cost you around $150 of take-home pay; a $200 post-tax deduction costs the full $200.
Which payroll deductions are pre-tax?+
Traditional 401(k) and 403(b) contributions, health, dental and vision premiums under a Section 125 plan, HSA and FSA contributions, dependent care FSA, and commuter benefits. Health premiums under a Section 125 plan also avoid Social Security and Medicare — traditional 401(k) contributions do not.
Is a Roth 401(k) a post-tax deduction?+
Yes. Roth contributions come out after tax, so they do not lower your current taxable income. The trade is at the other end: qualified withdrawals in retirement, including all investment growth, are tax-free, whereas traditional 401(k) withdrawals are taxed as ordinary income.
Do post-tax deductions reduce Social Security and Medicare tax?+
No. They come out after all taxes are calculated, so FICA is unaffected. Only certain pre-tax deductions reduce FICA — chiefly Section 125 health premiums, HSA contributions through payroll, and FSAs. Traditional 401(k) contributions reduce income tax but not FICA.
Are wage garnishments pre-tax or post-tax?+
Post-tax, always. Garnishments for child support, tax levies, student loan defaults and court judgments are calculated from disposable earnings — pay after legally required withholding — and come out after tax. Federal law caps how much can be taken, with the limits varying by garnishment type.
What are deductions on a paycheck?+
Everything subtracted between gross pay and net pay. They fall into three groups: taxes (federal income tax, Social Security, Medicare, state and local tax), pre-tax benefit deductions such as 401(k) and health premiums, and post-tax deductions such as Roth contributions, union dues and garnishments.
What is pre-tax income and how do I calculate it?+
Pre-tax income is your pay before tax is applied. To calculate pre-tax income for a paycheck, take gross pay and subtract only the pre-tax deductions — 401(k), Section 125 premiums, HSA and FSA. The result is the figure your tax is actually computed on, which is why the annual pre tax income in W-2 Box 1 is smaller than your salary. To find pretax income for a year, start from gross annual pay and subtract the year's pre-tax deductions.
Why does the order of deductions matter on a pay stub?+
Because each pre-tax deduction shrinks the base the next tax is calculated on. Payroll runs a fixed sequence: gross pay, then pre-tax deductions, then taxes on what remains, then post-tax deductions. A benefit moved from the post-tax group to the pre-tax group changes your tax, not just the label.