Flat tax

Flat tax, in plain terms

This tax applies directly to gross pay, reducing the final take-home pay by a constant percentage. It is distinct from social security or medicare withholdings, which serve different federal purposes and follow specific contribution caps. A flat tax is not a regressive tax, as the percentage remains stable, nor is it a complex bracket system that requires tiered calculations based on varying income thresholds throughout the fiscal year.

Flat tax on a real salary

Every figure below is produced by the same engine that runs the AfterTaxLab calculators — nothing here is estimated by hand.

Under a flat tax, the tax amount scales linearly with the base salary. For instance, Utah’s 4.55% flat rate takes $4,550 on a $100,000 salary. If the state rate differs, the liability changes accordingly, such as when Illinois takes $4,950 on the same pay. These figures represent the direct application of the state rate against the gross income, ensuring that every taxpayer pays a consistent portion of their earnings regardless of their specific total salary level.

Using flat tax on AfterTaxLab

The flat tax rate appears within the state tax section of the paycheck calculator. Users should look for the state-specific line item under the deductions summary. This field shows how your total gross income is reduced by the state flat rate to reach your final take-home pay estimate for a specific pay period.

Flat tax versus progressive tax: the arithmetic

The spread between flat states is the whole story. On the same $100,000 salary the 2026 engine charges $2,500 in Arizona (2.50%), $3,070 in Pennsylvania (3.07%), $4,550 in Utah (4.55%), $4,950 in Illinois (4.95%) and $6,000 in South Carolina (6.00%). Twenty-one states sit in that group, and nine more -- Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington and Wyoming -- levy no wage income tax at all, so the state line on the paycheque is $0.

Progressive states behave differently by design. California and New York are the two the engine models with real brackets, so the rate applied to the next dollar rises with income and two colleagues on $100,000 and $200,000 do not simply pay double the state tax. That is the arithmetic difference in one sentence: a flat tax is a straight multiplication, a progressive tax is a staircase.

What a flat tax does and does not touch

In the AfterTaxLab engine a flat state's liability is the rate applied to the salary you enter, which is why the amounts above scale in a straight line with pay. Whether a given state's real base is gross wages or some taxable-income figure is set out in that state's own tax code, so the engine labels every state with the model it used:

• zero -- no wage income tax (Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, Wyoming)
• flat -- a single rate on the whole base (Arizona 2.50% through to South Carolina 6.00%)
• estimate -- bracket systems modelled at an effective rate (Alabama, Ohio, Oregon, Virginia and 15 others)
• progressive -- a fully modelled staircase (California and New York)

Two things a flat rate leaves alone. FICA: Social Security at 6.2% on wages up to the $184,500 wage base and Medicare at 1.45%, plus 0.9% above $200,000, are federal payroll taxes charged before any state consideration. And the question of value: a flat rate is not automatically cheaper. At 6% a low earner gives up proportionally more than a 2.5% rate asks of a high earner, and because everyone pays the same percentage the honest comparison is always flat versus what -- which is why the calculator prints the state figure next to the federal one, side by side.