wage base
The income ceiling above which Social Security tax stops.
The annually indexed maximum of wages subject to Social Security tax.
What that means in practice
Social Security tax is charged on your wages up to a limit set each year. Past that point it simply stops, so a very high earner pays it on a smaller share of their income than someone earning less does. Medicare has no such ceiling.
The wage base caps the Social Security component of payroll tax, so the effective payroll rate declines above the threshold — the principal source of regressivity in the payroll system. ⭐ Crossing it produces one of the few points in the code where a taxpayer's marginal rate falls as income rises, and take-home on the next increment increases accordingly.
Questions people ask
Does this change depending on which state I live in?
No — payroll taxes are federal. wage base works the same in every state. It is one of the few parts of a paycheck that does not move when you do. That is why comparing take-home between states isolates the state layer so cleanly.
Is this one of those terms that needs three other terms to explain it?
Not really. wage base is fairly self-contained. You can understand it without first learning a chain of other definitions. That makes it a good place to start if the rest of the vocabulary is new.
I have seen this called something else. Is it the same thing?
Probably yes. wage base travels under several names. Forms, employers and news coverage each tend to use a different one for the same rule. That is a real source of confusion, not a trivial one. The alternatives are listed on this page.
Is this determined federally or by jurisdiction?
Payroll taxes are levied under federal law and apply uniformly across jurisdictions. Rates and thresholds are set by statute and adjusted annually where indexed. State income tax is separate and additive; it does not modify the payroll computation.
Does this term resolve independently?
This term resolves largely independently of other defined terms, with limited cross-references. It is therefore usable as an entry point; more heavily cross-referenced provisions generally require it rather than the reverse.
What alternative designations refer to this concept?
This concept is referred to by multiple designations across statutory text, agency guidance, payroll documentation and common usage. The alternatives are enumerated on this page. ⚠️ Terminology divergence is a frequent source of error where a statutory term and its colloquial equivalent are not exactly co-extensive.