The rates behind the calculators

PlainPound is an independent UK site offering free calculators for everyday money questions — maternity pay, take-home pay, and more to come. Each tool has its own page and answers one question properly rather than approximately.

Nobody funds it. No company sits behind it, nothing is for sale, and no bank, lender, pension provider or comparison site pays for a mention. There's no sign-up, no email capture and no premium tier holding a better answer back.

What follows is everything the tools assume, so you can check the working rather than take it on trust.

The personal allowance is the slice of income taxed at 0%. It currently stands at £12,570 and is frozen — so pay rises pull a slightly larger share of income into tax each year even when rates don't change.

England, Wales & N. Ireland	Rate
Up to £12,570 — personal allowance	0%
£12,571 to £50,270 — basic rate	20%
£50,271 to £125,140 — higher rate	40%
Over £125,140 — additional rate	45%

The allowance taper above £100,000

Earn over £100,000 and the personal allowance shrinks by £1 for every £2 above that line, disappearing entirely at £125,140. Because you lose tax-free income at the same time as paying 40% on the new earnings, the effective rate on that band is around 60% — the single most useful thing a calculator can point out, and the thing most calculators leave out. The taper is worked out on adjusted net income, so pension contributions and Gift Aid donations reduce it.

Scotland

Income tax on earnings is devolved. If you live in Scotland you get the same £12,570 personal allowance, but six bands rather than three:

Scotland	Rate
£12,571 to £16,537 — starter	19%
£16,538 to £29,526 — basic	20%
£29,527 to £43,662 — intermediate	21%
£43,663 to £75,000 — higher	42%
£75,001 to £125,140 — advanced	45%
Over £125,140 — top	48%

Figures assume the standard personal allowance. Scottish rates apply to employment and pension income only — savings interest and dividends are taxed at the same rates across the whole UK. National Insurance is not devolved.

Tax codes

Each calculator assumes the standard 1257L code and a full personal allowance. HMRC adjusts a tax code for all sorts of reasons — a company car, medical cover, tax owed from an earlier year — and a different code means a different answer. If yours isn't 1257L, the figures will differ — check the code on your payslip.

PAYE is cumulative

Payroll doesn't tax each month in isolation. It works out the tax due on your earnings so far this tax year and deducts whatever hasn't already been collected. That's why pay dropping mid-year — going onto maternity pay, say, or reduced hours — often produces a refund in the following payslip rather than simply a smaller deduction. The maternity pay planner models this month by month; most calculators don't attempt it.

Employee Class 1 NI	Rate
Up to £12,570 (£1,048/month)	0%
£12,571 to £50,270 (£1,048–£4,189/month)	8%
Above £50,270 (£4,189/month)	2%

Unlike income tax, National Insurance is worked out separately for each pay period and never reconciled across the year. A single large month — a bonus, or back pay — can therefore cost more NI than the same money spread evenly, and it isn't refunded later.

Employees over State Pension age don't pay Class 1 NI. Company directors are assessed on an annual basis instead, which the calculators don't model.

Plan	Threshold & rate
Plan 1	9% over £26,900
Plan 2	9% over £29,385
Plan 4 (Scotland)	9% over £33,795
Plan 5	9% over £25,000
Postgraduate	6% over £21,000

Your plan depends on where you lived and when your course started, not on which university you attended. A postgraduate loan sits on top of an undergraduate one, so it's possible to be repaying 15% of the earnings above both thresholds at once. Two undergraduate loans, by contrast, are collected as a single deduction and split behind the scenes.

Deductions are calculated per pay period, so an irregular month changes the amount taken. Interest is irrelevant to what leaves your payslip: it affects the balance, not the deduction.

Three arrangements are common, and each behaves differently on a payslip:

Salary sacrifice

You formally give up part of your salary and your employer pays it into the pension instead. Because your gross pay is genuinely lower, it reduces income tax, National Insurance and student loan repayments — which makes it the most efficient of the three, and the one that can pull income back under a threshold such as £100,000 or £50,270.

Net pay arrangement

The contribution comes out before income tax is calculated, so relief is given at your highest rate straight away. National Insurance and student loan deductions are unaffected.

Relief at source

The contribution is taken from pay after tax, and the provider claims 20% back from HMRC. A higher or additional rate taxpayer has to claim the rest back through a tax return, or by asking HMRC to adjust the tax code — a step that's easy to miss.

Where a tool offers salary sacrifice, it applies it before tax, NI and student loan are worked out. Employer contributions are ignored for take-home pay, because that money never passes through your payslip.

Period	Paid at
Weeks 1 to 6	90% of average weekly earnings
Weeks 7 to 39	£194.32/week, or 90% of AWE if lower
Weeks 40 to 52	Unpaid

Statutory maternity pay is taxable and subject to National Insurance like any other earnings. Average weekly earnings are set by what you actually earned in a reference period before the birth. The planner derives this from your salary, which tracks closely for steady pay; a bonus or unpaid time inside that window will shift it.

Many employers pay more than the statutory minimum for the early weeks. The planner handles both styles of enhanced scheme — one where employer pay includes the statutory amount, one where it sits on top — because the difference is worth thousands and contracts rarely spell it out clearly.

1. Verify the rates before any code is written

   Every threshold, band and weekly rate is checked against the primary source — HMRC, GOV.UK, gov.scot, or the legislation itself. Never another calculator.

2. Build the maths separately from the page

   The calculations are written and reasoned about in isolation, so a display problem can't quietly become a maths problem.

3. Test the maths against worked examples

   Scenarios are reconciled to the pound: annual totals, every band boundary, Scotland and the rest of the UK separately, each student loan plan including postgraduate.

4. Test the whole page, not just the sums

   The finished page is run start to finish the way you'd use it — enter figures, press the button, check the output. Nothing goes live without this step.

5. Date-stamp it, state the assumptions, publish

   Every tool shows its tax year and lists what it assumes, so you find out it doesn't fit your situation before you've spent five minutes on it.

All figures on this page are for the current tax year and are reviewed every April.

Where sources disagree, the legislation or the HMRC manual wins, and the tool's assumptions note records the choice.

Not financial advice

Every result is an estimate produced by applying published rules to the numbers you type in. It is general information, not a personal recommendation, and takes no account of your circumstances, your goals or your risk. PlainPound is not authorised or regulated by the Financial Conduct Authority, isn't connected to HMRC or any government department, and doesn't give regulated advice on pensions, investments, mortgages, insurance or debt.

If a decision is large or hard to undo, get advice from someone qualified to give it. MoneyHelper and Citizens Advice are free and impartial; for tax, an accountant or HMRC; for pensions and investments, an FCA-authorised adviser.

Situations outside the scope

A calculator here covers standard PAYE employment. The following sit outside that, and payroll will produce a different figure:

• Non-standard or emergency tax codes, or codes carrying an adjustment from an earlier year
• Benefits in kind — company cars, medical cover, taxable expenses
• More than one job at once, irregular pay, one-off bonuses, or directors' National Insurance
• Anything settled through Self Assessment rather than PAYE
• Means-tested benefits such as Universal Credit, which interact with income in ways a pay calculator can't model

Your employer's payroll and HMRC are the authority on what you're actually paid and taxed. Use these tools to work out what to expect — and what to ask about.

Accuracy and corrections

Every figure is checked against the primary source and every tool is tested end to end before it goes live, and again each April when rates change. Results are nonetheless provided without warranty, and no liability is accepted for decisions taken on the strength of a result. The sources above are listed so that anything important can be verified directly.

Nothing you type leaves your browser

Every calculator runs entirely on your own device. Your salary, your leave dates, your outgoings — none of it is sent anywhere, stored or logged, because there is nowhere for any of it to go. No accounts, no cookie banner, no tracking scripts. The only measurement attached to the site is Google Search Console, which reports anonymous search statistics and never sees what you enter.

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