“Deductions” on a pay stub is one block that contains three different kinds of thing, and they do different work. Some of them reduce the pay you are taxed on. Some of them are the tax. Some of them are simply bills the employer settled on your behalf. Reading a stub — or writing one that will survive a second pair of eyes — means knowing which line is which.
The three categories
- Pre-tax. Taken out before income tax is calculated, so they lower the wages withholding is applied to. Typical examples: a health, dental or vision premium paid through a cafeteria plan, HSA contributions, commuter benefits, and traditional 401(k) elective deferrals.
- Statutory. Required by law rather than elected by you: federal income tax withholding, Social Security and Medicare (together FICA), and state or local income tax where those exist.
- Post-tax (voluntary or directed). Deducted after tax, from what is left: Roth contributions, union dues, life or accident insurance bought with after-tax dollars, charitable giving, wage garnishments and child support orders.
The part most explanations get wrong
“Pre-tax” is not one switch. A traditional 401(k) deferral reduces the wages that federal income tax is computed on, but it remains subject to Social Security and Medicare — the deferral is still FICA wages. A Section 125 health premium, by contrast, drops out of both. So two stubs with the same gross and the same total deductions can legitimately show different FICA figures, depending on which lines sit in which category.
The employer’s obligations, meanwhile, never appear in your deduction block at all. The matching employer share of Social Security and Medicare, federal and state unemployment taxes, and workers’ compensation are reported and paid by the employer — see the IRS Employer’s Tax Guide for the rules, and Form 941 for the quarterly return on which those amounts are reported. A stub that shows you being charged an “employer” tax line is a document worth questioning.
A worked example, with the bases shown
Gross pay of $3,000.00 for a bi-weekly period. A health premium of $180.00 under a cafeteria plan, and a 401(k) deferral of 5% ($150.00). Then taxes, then one post-tax line:
| Line | Amount | Which base it changes |
|---|---|---|
| Health premium (pre-tax) | $180.00 | Income-tax wages and FICA wages both drop to $2,820.00 |
| 401(k) deferral (pre-tax) | $150.00 | Income-tax wages drop to $2,670.00; FICA wages stay $2,820.00 |
| Social Security at 6.2% | $174.84 | Computed on $2,820.00 |
| Medicare at 1.45% | $40.89 | Computed on $2,820.00 |
| Federal withholding (illustrative) | $310.00 | From the tax tables applied to $2,670.00 and the W-4 on file |
| State income tax (illustrative) | $120.00 | Its own rules, often close to the federal base |
| Union dues (post-tax) | $25.00 | Nothing — taken from what is left |
| Total deductions | $1,000.73 | The sum of the seven lines above |
| Net pay | $1,999.27 | $3,000.00 minus $1,000.73 |
Only the two percentages that are set by statute were calculated here. The withholding figures are illustrative placeholders, deliberately: they come from tables, brackets and a W-4 picture that changes per person, and any article that hands you a flat number is guessing.
What no generator can do for you
This site does not compute withholding, and neither should you trust a tool that claims to. What it does is arithmetic and presentation: the deduction rows are yours — up to 20 of them, each with a short label and an amount — and the pay stub builder adds them, subtracts them from gross, and prints the result. If you are paying a person, the numbers you enter have to come from a payroll system, a provider, or your own reading of the rules; the document here is the record of that decision, not the source of it.
Two practical consequences. First, list deductions one per line with names a reader can map to real obligations — the field-by-field template guide shows what a clean block looks like. Second, if a reader needs year-to-date figures or per-tax breakdowns, that is a payroll report, not a stub; the difference between those records is exactly what the three-documents comparison covers.
And for the question this section always raises — whether an employer may deduct something at all, and what the paperwork is for — the disclaimer states the line this site draws, and the home page questions cover what happens to the file once it has been paid for.