Pension tax relief calculator — methodology

Why it is a difference and not a multiplication

The intuitive formula is relief = contribution × marginal rate. It is right often enough to be dangerous and wrong in three places that matter:

• A contribution that crosses a band boundary. Only the income actually being charged at the higher rate can be moved out of it. On £60,000, £10,000.00 is relieved at 39.46% rather than the whole higher rate, because part of it runs off the bottom of that band.
• A contribution inside the personal allowance taper. It restores allowance as well as being relieved, and the two compose.
• Scotland, twice over: more bands move, and the statute that moves them is a different subsection.

relief claimed = tax(income) − tax(income with the contribution)
relief at source = contribution × the basic rate      (relief at source only)
total relief     = relief at source + relief claimed
cost to you      = contribution − total relief

Both tax figures come from computeTaxPosition, the same function behind every income tax page on this site, so this page cannot disagree with them.

The two mechanisms, and only one of them moves a band

Relief at source — personal pensions, stakeholder pensions, SIPPs. The member pays out of taxed income and the scheme reclaims the basic rate from HMRC: £80.00 handed over becomes £100.00 in the pot, with £20.00 reclaimed. Note the arithmetic: the gross figure is the net one divided by one less the rate, not multiplied by one plus it. Relief above the basic rate is not paid to the scheme at all — it is given by increasing the rate limits.

A net pay arrangement — most occupational schemes. The employer deducts the contribution before operating PAYE, so taxable pay is lower and relief happens at the member’s own rate automatically. No band moves, because nothing needs to: the income never enters the higher band in the first place.

Neither of them is salary sacrifice, and net pay looks identical to sacrifice on a payslip. A net pay contribution is still the employee’s earnings for National Insurance, so neither employee nor employer National Insurance falls; a sacrifice reduces gross pay itself, so both do. Presenting net pay as though it saved National Insurance overstates it by the employee rate on the whole contribution.

Which limits a contribution increases

Finance Act 2004 s.192(4), for England, Wales and Northern Ireland:

...the basic rate limit and the higher rate limit for the tax year in the
individual's case, are increased by the amount of the contribution.

and s.192(4A), for a Scottish taxpayer:

...the Scottish basic rate limit, and any other Scottish rate limit for the
tax year in the individual's case that is above the Scottish basic rate
limit, are increased by the amount of the contribution.

The two read differently and mean the same shape: every limit from the top of the basic rate band upwards moves, and nothing below it does. That last exclusion is invisible in the headline case and wrong by a whole percentage point in another — extending Scotland’s starter-rate ceiling as well would give an intermediate-rate taxpayer two points of extra relief where gov.uk publishes one.

Each moved limit shifts a slice of income down one band, and the shifts compose. On £200,000 in England, the higher rate limit moving is worth one slice and the basic rate limit moving is worth another, and the total comes to 45.00% of the contribution — which is the figure gov.uk publishes for income taxed at the additional rate. The cascade is the answer rather than an artefact of it.

The personal allowance a contribution buys back

Above £100,000 the personal allowance is withdrawn by £1 for every £2 of income. The measure it is withdrawn against is adjusted net income, and gov.uk’s guidance is explicit that a grossed-up relief-at-source contribution is deducted in arriving at it. So a contribution in that range runs the withdrawal backwards.

On £110,000 in England, £10,000.00 restores £5,000.00 of personal allowance, and the relief comes to 60.00% of the contribution: the band rate on the contribution, plus the same band rate on the allowance it handed back. In Scotland the identical contribution at the identical income is relieved at 67.50%, because the band rate there is different.

Neither percentage is written anywhere in this software. Both are measured against the rate schedules for the year, which is the only way one page can carry both régimes without being wrong for one of them. It is also the effect most easily dropped, because nothing about it reads as “pensions”: it is the difference between a higher-rate taxpayer getting the band rate and getting half as much again.

Two limits, and this page applies one of them

FA 2004 s.190 caps the relief at the greater of relevant UK earnings and the basic amount of £3,600. Contribute beyond it and the excess simply gets nothing. This page applies that limit and reports the unrelieved part separately.

The annual allowance caps tax-privileged saving. Exceed it and the contribution is relieved in full and then charged back through a separate tax charge at the member’s marginal rate. It counts employer contributions and salary sacrifice, and it is tapered for high earners. This page does not apply it, and says so next to the answer rather than here, because a page that showed one of the two and called it “the limit” would tell somebody the wrong thing about the same pound.

Relevant UK earnings are not the same as income. Pensions in payment, the state pension, rental income and taxable benefits are all taxed on the earned schedule and none of them are relevant UK earnings — which is why the calculator asks rather than assuming, and why the engine refuses to default the figure at all.

Rates, thresholds and allowances

The rate given at source is read off the named band rather than stored as a second figure, so it cannot drift from the rate the same schedule charges. Every threshold in the table is taxable income, after allowances.

Sources

• gov.uk — Tax on your private pension contributions: pension tax reliefThe taxpayer-facing statement of both mechanisms, the limit on relievable contributions, and the extra relief claimable at each band in the rest of the UK and in Scotland. Those published percentages are the check on whether the band extension comes out right.
• HMRC — Pensions Tax Manual PTM044220, relief at sourceThat the provider reclaims the relevant rate and that relief above it is given by the member’s tax office. It works the arithmetic and does not state the mechanism; the mechanism comes from the statute below.
• Finance Act 2004 s.192 — relief at source and the rate limits it increasesSubsection (4) increases the basic rate limit and the higher rate limit; (4A) increases the Scottish basic rate limit and every Scottish limit above it. The two read differently and mean the same shape, and the difference decides what a Scottish taxpayer gets.
• Finance Act 2004 s.190 — the limit on relievable contributionsRelief is capped at the greater of relevant UK earnings and the basic amount. This is not the annual allowance.
• gov.uk — Adjusted net incomeThat a grossed-up relief-at-source contribution is deducted in arriving at adjusted net income, which is the measure the personal allowance taper is applied to. This is the step that produces the relief rate inside the taper.
• gov.uk — Pension annual allowanceThe other limit, named here because a page showing one of the two and calling it “the limit” misleads about the same pound. It is not applied on this page.
• gov.uk — Income tax rates and allowances: current and past
• 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.

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

• The annual allowance, its taper, the money purchase annual allowance and carry forward. A different limit with a different consequence, and the one that costs money to breach rather than merely wasting a contribution.
• Whether the relief that has to be claimed is ever claimed. Under relief at source only the basic rate arrives on its own. The rest reaches the member through Self Assessment or a tax code adjustment, nothing prompts it, and HMRC has said repeatedly that a great deal of it is never claimed. Every figure here is what the rules allow, not a record of what anybody received.
• Employer contributions. Relieved to the employer rather than to the member, and they move none of the member’s rate limits. They do count towards the annual allowance, which is another reason the two limits are not interchangeable.
• Savings interest, dividends and capital gains. A relief-at-source contribution extends the savings and dividend limits too, and widens the lower capital gains band. This page has one income field and applies the contribution to the earned schedule only, so a reader with investment income has more relief than it shows.
• Gift aid, which increases the same rate limits by the grossed-up donation and therefore interacts with everything above.
• Contributions to overseas schemes, migrant member relief and the transitional protections, none of which are in the engine.