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After-Tax (Post-Tax) Deduction
After-Tax (Post-Tax) Deduction paystub meaning: A deduction taken after tax has already been calculated, so it lowers your take-home pay without lowering...
A deduction taken after tax has already been calculated, so it lowers your take-home pay without lowering the wages you were taxed on.
An after-tax deduction is subtracted from your pay after federal income tax, state income tax, Social Security and Medicare have already been figured. It lowers none of them. It lowers only the number at the bottom of the stub. The order of operations is visible if you look for it: gross pay, minus pre-tax deductions, gives the wages each tax is computed on; taxes are withheld; then after-tax items come out of what is left; the remainder is net pay. Two identical $200 deductions, one pre-tax and one after-tax, do not cost the same amount of take-home pay. What normally lands in this column: - Designated Roth 401(k) contributions. The IRS instructions for Forms W-2 and W-3 state that designated Roth contributions are subject to federal income tax withholding and to Social Security and Medicare taxes, and are reported in boxes 1, 3 and 5. Roth and traditional share one ceiling — $24,500 of elective deferrals for 2026 across both, not $24,500 each. - Union and association dues. - Voluntary life insurance you buy above the employer-provided amount, and most AD&D coverage. - Wage garnishments and child support orders, which are involuntary and legally capped. - 401(k) loan repayments, employee stock purchase plan contributions, and payroll charitable giving. One timing note: under the SECURE 2.0 Act, catch-up contributions by higher-paid participants must be made on a Roth basis. The IRS final regulations generally apply for tax years beginning after 31 December 2026, and permit plans to use a reasonable, good-faith interpretation before then — so some 2026 stubs already show a catch-up flipped to Roth.
A deduction can be pre-tax, post-tax, voluntary, or required. Its label alone does not establish how it affects taxable wages, so check the plan document, employee election, payroll policy, and year-to-date amount.
When this term appears on a statement, read its label, current amount, year-to-date amount, pay-period context, and any adjacent rate or hours together. Resolve a mismatch with the original issuer or the cited authority rather than changing a record to force a preferred result.
Example
$4,000 semi-monthly gross, with a $200 Roth 401(k) contribution and $45 in union dues. Roth money is after-tax, so the wage base for FICA is still the full $4,000. Social Security is $4,000 × 6.2% = $248.00. Medicare is $4,000 × 1.45% = $58.00. Now the comparison that makes the point. Had that same $200 gone into a traditional 401(k) instead, your federal income tax wages would have dropped from $4,000 to $3,800 — but Social Security and Medicare would still have been calculated on $4,000, so $248.00 and $58.00 would not have changed by a cent. The Roth choice costs income tax today; it never costs extra FICA, because the traditional route would not have saved any. The $200 and the $45 then come out after the taxes, reducing your deposit by $245 without reducing any tax.
Source: IRS — General Instructions for Forms W-2 and W-3
Related terms
- Pre-Tax Deduction — A deduction taken before tax is calculated — but it does not lower every tax, and which ones it lowers depends on the benefit.
- Wage Garnishment — A court or agency order forcing your employer to withhold part of your pay for a debt, capped by federal law at a percentage of disposable earnings.