How a progressive bracket schedule actually works.
A progressive system taxes successive slices of income at successively higher rates. The arithmetic is straightforward; the political and behavioural consequences are not.
The mechanism
Income is divided into bands by threshold. Each band has a fixed rate. Income within a band is taxed at the band's rate, regardless of where the rest of your income sits. The total tax is the sum of (income in each band × rate of that band), with credits and reliefs applied either before bracket-walking (deductions) or after (credits).
This produces a tax curve that is everywhere monotonically non-decreasing in income (subject to the edge cases noted below). Marginal rate steps up at each threshold; effective rate rises smoothly toward the top marginal rate without ever reaching it.
Why progressive?
Three justifications appear in the academic and political literature, in roughly descending order of empirical support:
- Diminishing marginal utility of income. The hundredth euro of monthly income produces more welfare than the ten-thousandth euro. Taxing higher incomes more heavily (in absolute terms) produces less aggregate welfare loss than taxing lower incomes the same proportion.
- Ability to pay. Households with higher disposable income have greater capacity to bear tax obligations without affecting basic consumption.
- Redistribution. An explicit social-policy goal in many jurisdictions, separate from the welfare or ability-to-pay arguments.
Reference: top marginal rates across major economies, 2025
| Country | Top marginal rate (income tax + social) | Threshold (above) |
|---|---|---|
| Sweden | ~57% | SEK 643,100 |
| Denmark | ~56% | DKK 588,900 |
| France | ~55% (incl. CSG/CRDS) | €177,106 |
| Belgium | ~54% | €48,320 |
| Ireland | ~52% (incl. USC, PRSI) | €70,044 |
| Netherlands | ~49.5% | €73,032 |
| Germany | ~47.5% | €277,826 |
| UK | ~47% (top rate + employee NI) | £125,140 |
| US (federal only) | 37% | $609,350 |
| US + California | ~50% combined | $1,000,000 |
| Singapore | 24% | S$1,000,000 |
| Hong Kong | 17% (cap) | N/A flat above ~HK$2m |
The variation is striking: top marginal rates in continental Europe sit at roughly twice the level of the East Asian financial centres. The threshold at which the top rate kicks in also varies enormously, which materially changes who actually pays it.
The edge cases that produce non-monotonic effective rates
Most progressive systems have small zones where the effective marginal rate exceeds 100 % — that is, an extra euro of gross income produces less than zero of net income. These are typically caused by means-tested benefits or allowance tapers that withdraw benefits faster than the new gross can replace them.
- UK personal allowance taper (£100,000–£125,140). The personal allowance is withdrawn at 50p per £1 of income, producing an effective marginal rate of 60 % over this range vs. the headline 40 %.
- UK child benefit clawback (above £60,000 for the higher earner). For families with multiple children, the marginal rate over the clawback range can exceed the headline rate by 8–15 percentage points.
- US Social Security taxation on retirement benefits has “tax torpedo” ranges where each additional dollar of pension income causes additional Social Security to become taxable, producing effective rates well above the bracket nominal.
The calculator does not currently model these edge cases. For income ranges that cross known taper boundaries, consult a tax adviser.
Alternatives
- Flat tax. A single rate applied to all income (often with a personal allowance). Implemented in several Eastern European countries (Estonia 20 %, Latvia 20 %, Lithuania 20 %) and a handful of smaller economies. Simpler administration; weaker redistributive effect.
- Regressive consumption tax. Tax based on spending rather than income, with no progressive structure. VAT is the workhorse example; it falls more heavily on lower-income households who spend a higher share of income on consumption.
- Progressive consumption tax. Theoretical alternative discussed in academic literature, never implemented at national scale. Would tax consumption above thresholds analogously to bracket-walked income tax.