How tax bands actually work
Moving into a higher band does not tax all of your income at the higher rate. Here is the arithmetic, and the three different rates people mix up.
Two ideas about income tax are widely believed and both are wrong. The first is that crossing into a higher band taxes everything you earn at the higher rate. The second follows from it: that a pay rise can leave you with less money. Neither is true under a progressive system, and the arithmetic that shows why is worth seeing once.
Each rate applies only to its own slice
A progressive system divides income into bands and charges each band its own rate. Income inside a band is taxed at that band's rate; income above it moves into the next band and is taxed there. Nothing reaches back and re-taxes what came before.
So on a UK salary of £60,000 for 2026 to 2027: the first £12,570 is covered by the Personal Allowance and taxed at nothing. The next £37,700 is taxed at 20%, which is £7,540. Only the remaining £9,730 meets the 40% rate, which is £3,892. The total is £11,432 — not the £24,000 that 40% of the whole salary would be, and not anywhere close to it.
This is why our calculator prints every band as its own line with the amount inside it. The single total tells you what you owe; the lines tell you why, and correct the misunderstanding without needing to argue about it.
Marginal and effective are different numbers
Your marginal rate is what the next pound you earn will be taxed at. In the example above that is 40%. It matters when you are deciding about overtime, a bonus or a pension contribution, because it is the rate that applies to the change.
Your effective rate is the tax you actually pay as a share of everything you earned. On £60,000 with £11,432 of tax that is about 19% — less than half the marginal rate. It is the honest answer to "how much tax do I pay", and it is always lower than the marginal rate whenever any of your income sat in a lower band.
People quote the marginal rate when they mean the effective one constantly, usually when complaining. Both are real; they answer different questions.
A third number, which is not a tax rate at all
Take-home pay is reduced by more than income tax. National Insurance in the UK, the Medicare levy in Australia, and their equivalents elsewhere are separate charges with their own thresholds and their own rates, and they are not income tax.
Adding them together produces a total deduction rate, which is a useful figure and a misleading one if it is labelled as tax. Our calculator shows both, separately, for exactly that reason. A page that folds contributions into "your tax rate" is overstating income tax, and it is a common way to make a headline sound worse than the position it describes.
Can a pay rise ever leave you worse off?
Not through the bands themselves. Because each rate applies only to the income inside its band, an extra pound is always taxed at your marginal rate, and a marginal rate is always below 100%. More gross income is always more net income.
What can genuinely bite is a cliff — a threshold where something is withdrawn all at once rather than gradually. Those exist, in means-tested benefits, in childcare support, in student loan thresholds, and they are separate from the tax bands. The UK's Personal Allowance withdrawal above £100,000 is a taper rather than a cliff, but a steep one: the allowance falls by £1 for every £2 earned above the threshold, which produces an effective marginal rate of 60% across that range before it returns to 45%. It is still not a loss — you keep 40% of every pound in that stretch — but it is much less than the headline rate suggests, and it is real.
The American version: brackets, and the two things that aren't brackets
American tax talk uses "tax bracket" the way British tax talk uses "band", and it works identically: the 22% bracket does not mean 22% of everything, it means 22% of the slice of taxable income that falls inside it. A single filer in 2026 with $83,900 of taxable income pays 10% on the first $12,400, 12% on the next $38,000, and 22% only on the $33,500 above $50,400 — $13,170 in total — 15.7% of that taxable income, not 22%, and 13.2% of a $100,000 salary once the standard deduction is counted.
Two American deductions are frequently mistaken for brackets, and neither is one. The standard deduction — $16,100 single or $32,200 married filing jointly in 2026 — comes off before any bracket applies, which is why "taxable income" and "salary" are different numbers and why quoting a bracket against a gross salary overstates the tax. And FICA is not a bracket at all: Social Security is a flat 6.2% that stops dead at the $184,500 wage base, Medicare is a flat 1.45% that never stops, and both are charged on gross wages rather than on taxable income, so the standard deduction does not reduce them. A high earner's Social Security contribution therefore falls as a share of their pay the more they earn, which is the exact opposite of how a progressive band behaves.
Filing status is the other American wrinkle. It does not adjust one number; it swaps the whole schedule. The 24% bracket starts at $105,700 of taxable income for a single filer and at $211,400 for a couple filing jointly, so the same household income lands in different brackets depending on how the return is filed.
Why the tax year is not just a year
One more thing worth knowing before comparing calculators. A "2026 tax calculator" means five different things depending on where you are. The UK's year runs from 6 April to 5 April. Australia's income year runs from 1 July to 30 June and is written 2026–27. Singapore assesses in YA 2026 the income you earned during 2025. India distinguishes the financial year from the assessment year that follows it. The United States and Canada use the calendar year, so a US "tax year 2026" figure is the one filed in early 2027.
A calculator that just says "2026" has not told an Australian or a Singaporean user which rules it used. Ours states the period's own label, the dates it actually covers, and the date each rate was last checked against the authority that sets it.
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