Take home pay calculator Scotland — methodology

The calculation, in order

1. Start from the gross annual salary.
2. Deduct the personal allowance that applies to it. It is a UK figure, not a Scottish one, and above £100,000 it is withdrawn at £1 for every £2 of income.
3. Charge the remainder across the six Scottish bands. Devolved.
4. Charge employee Class 1 National Insurance on the whole salary — the personal allowance does not touch it. Not devolved.
5. Subtract both. That is take-home pay.

taxable income = salary − personal allowance(salary)
income tax     = schedule[scotland].earned applied to taxable income     (devolved)

national insurance = mainRate  × (min(salary, upper earnings limit) − primary threshold)
                   + upperRate × max(0, salary − upper earnings limit)   (UK-wide)

take-home      = salary − income tax − national insurance
a month        = take-home ÷ 12
a week         = take-home ÷ 52

The National Insurance line is written out to show the shape of the charge, not because the page computes it: employeeNI does, and the calculator renders the bands that function returns. The two division lines are done here, and the page says so rather than presenting them as a payslip.

Two bases, and why conflating them is the classic error

Income tax is charged on income after the personal allowance. National Insurance is charged on gross pay from its own primary threshold, and nothing that changes the personal allowance changes it: not the taper, not a marriage allowance transfer, not a tax code carrying a benefit in kind.

For 2026/27 the two happen to begin at the same £12,570, which makes them look like one threshold. They are two, they have moved independently before, and the software keeps them apart: `computeTaxPosition` receives a region and `employeeNI` receives none, because there is no region for it to take.

The band that only exists in Scotland

The Scottish higher rate on earned income begins at a lower salary than the National Insurance upper earnings limit of £50,270. Between those two points a pound of pay meets the Scottish higher rate and the main National Insurance rate at once. On the salary this calculator opens with, £45,000, that is 42.00% plus 8.00% — 50.00% of the next pound.

In the rest of the UK the higher-rate threshold and the upper earnings limit sit at the same salary, so the stretch does not exist: income tax steps up at exactly the point National Insurance steps down. In Scotland the step down comes later, and the combined marginal rate therefore falls as pay passes the upper earnings limit — which is why the worked example on the calculator page can show a better-paid employee keeping more of the same pay rise.

Student loan repayments, which are worked out differently from both

A loan repayment is not a tax and is not calculated like one. Three things about it differ from the two deductions above, and all three change the answer.

It is charged on your pay, not on your taxable pay. HMRC uses the same gross earnings figure as the employer’s secondary Class 1 National Insurance. So a pension contribution under a net pay arrangement, which reduces taxable pay, does not reduce a loan repayment at all — while salary sacrifice, which reduces the earnings themselves, reduces the repayment along with the tax and the National Insurance. Neither is modelled on this page.

It is worked out on each pay packet separately, and never cumulatively. Nothing carries forward from one pay day to the next. A pay packet below the threshold simply has no deduction; it does not bank unused threshold for a later one, and it is not reclaimed at the end of the year.

Each pay packet is rounded down to a whole pound. HMRC’s specification gives the calculation as the pay above the periodic threshold multiplied by the recovery rate, “rounded down to the pound”. Because that happens once per pay day rather than once per year, twelve monthly repayments do not add up to one annual repayment on the same salary — and a weekly payroll rounds fifty-two times rather than twelve. That is why this page asks how often you are paid.

The periodic threshold is HMRC’s published weekly or monthly figure where one exists, and otherwise the annual threshold divided by the number of pay periods and rounded down to the penny — the rule the payroll specification gives. The two agree for every plan in both tax years this calculator models, which is asserted rather than assumed.

What the page divides is the annual salary you entered, by the number of pay periods. That carries the same caveat as the month and week columns above: a real pay packet containing a bonus is not a twelfth of a year, and a real payroll would use the actual pay.

Rates, thresholds and allowances

Every National Insurance figure in that table is UK-wide, and every one of them is HMRC’s published annual threshold rather than a weekly figure multiplied by 52. The same gov.uk table publishes both and they disagree by enough to change an answer; the annual figure is the one that governs an annual calculation, and `packages/tax-core/VERIFICATION.md` records the trap.

Sources

• gov.uk — Income tax in ScotlandWhich income the Scottish rates apply to, and that where you live rather than where you work decides it.
• gov.scot — Scottish income tax rates and bandsThe published page still titles its table “Proposed Bands”. The bands are in force: the Scottish Parliament agreed the Scottish Rate Resolution, motion S6M-20844, on 19 February 2026, and the resolution is the legal authority for the figures used here.
• gov.uk — Rates and thresholds for employersHMRC’s published ANNUAL National Insurance thresholds, which are deliberately not the weekly figures multiplied out.
• gov.uk — National Insurance rates and categoriesThe category A employee rates this calculator uses.
• gov.uk — Student and postgraduate loan deduction tables (SL3)The published annual, monthly and weekly repayment thresholds for every plan, and the recovery rates. Plan 5 appears for the first time in 2026 to 2027; the 2025 to 2026 tables list no Plan 5 because its first repayments fell on 6 April 2026.
• gov.uk — Collection of student loans from 6 April 2026HMRC’s payroll specification: the deduction is (earnings less the periodic threshold) times the rate, rounded down to the pound, worked out per pay period and not cumulatively. The periodic threshold is the annual one divided by the periods in the year, rounded down to the penny.
• gov.uk — Student loan repayment guidance for employersThat the earnings figure is the same gross pay used for the employer’s secondary Class 1 National Insurance, and the worked example this page’s arithmetic is checked against: £700 a week on Plan 1 gives £16, and £2,800 a month gives £50.
• gov.uk — Which repayment plan you are onThe checker this page links to rather than reproducing. Which plan a borrower repays on depends on the funding body and the course start date, not on where they live now.
• gov.uk — Income tax rates and allowances: current and pastThe personal allowance and its taper, both reserved to the UK Parliament.

Five things this calculation does not model, stated here rather than buried

• The student loan behind the repayment. The deduction is modelled for every plan, including Plan 4 — see the section above for how. The balance, the interest charged on it, the write-off date and any projection of when it clears are not, and will not be: a student loan is written off after a set period and is enforceable only against income, so presenting it beside a mortgage as a debt to clear would mislead more than it explained.
• Pension contributions. computeTaxPosition takes a pension contribution and extends the rate limits for relief at source, but this page passes neither. Auto-enrolment reduces net pay below the figure shown; a net pay arrangement also reduces the income tax; salary sacrifice reduces the National Insurance too. None of the three is here, and they do not all push the answer the same way.
• Tax codes. The standard personal allowance is assumed. A benefit in kind, an underpayment collected through PAYE, a marriage allowance transfer or a blind person’s allowance all move it. The S prefix that tells an employer to operate Scottish rates is set from the address HMRC holds, and a stale one is a common payroll error.
• Pay periods. Both engines are annual. Real PAYE is cumulative across the tax year and real National Insurance is worked out per pay period and is not cumulative for most employees, so the monthly column is an average rather than a forecast of any particular payslip. On £45,000 the annual take-home of £35,523.55 divides to £2,960.30 a month, and a month with a bonus in it will not look like that.
• Anything beyond one employment. No second job, no self-employed profit alongside the salary, no savings interest or dividends — those are charged on UK-wide bands and the Scotland tax calculator handles them — and no employer National Insurance, which is a cost of employing you rather than a deduction from your pay.