This page works the question underneath the recent rule changes: at what point do extra pension contributions stop earning their keep against an ISA? It exists because the answer is not a slogan in either direction. A pension stacks five separate advantages, they switch off one at a time as circumstances change, and the expensive mistakes sit at both ends: paying in blindly past the point the advantages stopped, and stopping entirely while the biggest one still applies.
Both wrappers share the big one: growth and income inside are untaxed. On top of that shared base, a pension adds four more, and each one has its own off switch.
| Advantage | What it is worth (2026/27) | Its off switch |
|---|---|---|
| Tax-free growth (shared with ISA) | No tax on growth or income inside the wrapper | Never switches off |
| Income tax relief | £80 becomes £100 at basic rate; £60 becomes £100 at higher rate | Weakens when the tax rate paid in retirement approaches the relief rate received |
| Employer match | Free money: a matched £1,000 is £2,000 invested before relief even starts | Stops at the employer's matching ceiling |
| National Insurance saving (salary sacrifice) | Sacrificed pay avoids employee NI: 8% at basic rate, 2% above | Enacted Capped from April 2029: only £2,000 a year of sacrificed contributions keep NI relief |
| 25% tax-free cash | A quarter of withdrawals free of income tax, within the £268,275 lifetime allowance | Stops adding value once the pot is on track past £1,073,100 |
| Outside the estate | Historically, unused pensions passed free of IHT | Enacted Switches off 6 April 2027: pensions join the estate (Royal Assent March 2026) |
The whole decision lives in that third column. Each switch that flips is a signal to look closer, not an instruction to stop, because the advantages work as a stack: one going quiet says little while the others still apply. The way to see the stack clearly is to follow a single £1,000 through it.
£1,000 of take-home pay, invested identically in each wrapper, growth set aside so only the tax mechanics show. "Spendable" is what comes out after the tax on withdrawals, with 25% drawn tax-free where available.
| Route | Relief going in | Effective tax coming out | Spendable | vs ISA |
|---|---|---|---|---|
| ISA | none | 0% | £1,000 | baseline |
| Pension, basic-rate relief, withdrawals inside the personal allowance | 20% | 0% | £1,250 | +25% |
| Same, via salary sacrifice | 28% | 0% | £1,389 | +39% |
| Pension, basic-rate relief, basic-rate tax on withdrawals | 20% | 15% | £1,063 | +6% |
| Same, via salary sacrifice | 28% | 15% | £1,181 | +18% |
| Same, plus a full employer match | 28% + match | 15% | £2,361 | +136% |
| Pension, higher-rate relief, basic-rate tax on withdrawals | 40% | 15% | £1,417 | +42% |
| Pension, higher-rate relief, higher-rate tax on withdrawals | 40% | 30% | £1,167 | +17% |
Two rows deserve a hard stare. The match row: £2,361 against £1,000 is why stopping pension contributions entirely is almost never right while an employer match is on the table, whatever else changes. And the +6% row: a basic-rate saver with no match and no salary sacrifice, who will pay basic-rate tax on withdrawals, is barely ahead of an ISA, and is paying for that 6% with locked-up money and exposure to whatever rules arrive over the next 20 years. Same wrapper, same saver's instinct, completely different deals.
Information and guidance only. Not personal advice. The table shows tax mechanics at 2026/27 rates for illustrative routes; real outcomes depend on income, employer scheme design and future rules. Investment values can fall as well as rise. Verify decisions with a qualified FCA-authorised adviser before acting.
Each of these is a point where one advantage in the stack switches off. None of them alone says stop; the third one usually does.
Signal one: the pot is on track past £1,073,100. Tax-free cash is capped at £268,275 in a lifetime, which is 25% of £1,073,100. A pension already projected to cross that line by retirement earns no additional tax-free cash from new contributions: the 25% advantage has switched off for every further pound. Two cautions before acting on it. Projections lean on growth assumptions, and a couple of weak market years can un-cross the line, so switching the tap off early risks being wrong in the expensive direction. And relief alone can still justify contributing: 40% relief in against basic-rate tax out is a +42% deal with no tax-free cash involved at all.
Signal two: the relief margin has gone thin. The clearest case: a basic-rate saver, match already captured, no salary sacrifice benefit, who will have a full state pension from 67. The state pension (£12,548) consumes all but £22 of the personal allowance (£12,570), so pension withdrawals beyond tax-free cash are taxed at basic rate from the first pound. That is the +6% row above. Six percent is not nothing, but it is thin enough that the ISA's advantages with no strings, access at any age, immunity to pension-rule changes, simplicity, are a respectable trade. This is the honest home of the diversify-across-wrappers argument: it gets stronger as the pension's margin gets thinner.
Signal three: the annual limits are breached. Contributions above the annual allowance (£60,000, tapered as low as £10,000 for the highest earners), above unused carry-forward from the past three years, above relevant earnings (someone earning £30,000 can contribute at most £30,000), or after the £10,000 MPAA has been triggered by a flexible withdrawal, attract tax charges that undo the relief. This is the one signal that means dial back rather than look closer.
One addition the signals miss because they are single-person: the partner's stack. A household's spare £1,000 belongs wherever the stack is tallest, and a partner with an uncaptured match, a higher relief rate, or unused allowances can be a better home for it than the pension it was habitually going to. The comparison has to be run per person; habit does not run it at all.
Enacted From 6 April 2027, unused pensions count in the estate for inheritance tax. The headline coverage says pensions are now "double taxed". The worked version is more interesting.
| £1,000 of take-home saved by a higher-rate taxpayer, left to a non-spouse heir | Heir ends up with | vs ISA |
|---|---|---|
| ISA: 40% IHT, wrapper dissolves at death | £600 | baseline |
| Pension (£1,667 pot after relief): 40% IHT, death before 75, heir draws tax-free | £1,000 | +67% |
| Same, death after 75, heir pays basic rate | £800 | +33% |
| Same, death after 75, heir pays higher rate (the "64% double tax" headline) | £600 | identical |
The pattern worth sitting with: even in the worst case, where IHT and a higher-rate heir stack to a combined 64%, the pension heir ends up exactly where the ISA heir does, because the relief on the way in grossed the pot up by the same arithmetic the tax on the way out takes back. Every better case (death before 75, an heir in a lower band, grandchildren drawing within their personal allowances over several years) tilts the pension ahead. The old rules were better; the new rules are not automatically a reason to redirect contributions.
For those whose real question is avoiding IHT rather than comparing wrappers, the honest answer has not changed: spend it or give it away. There the wrappers differ in a quieter way. ISA gifts are simple but start the seven-year clock. Pension income drawn at a lower rate than the relief received, and given away as regular gifts from surplus income, can qualify for the normal-expenditure-out-of-income exemption and leave the estate immediately, with no seven-year wait. The rules on that exemption have real conditions (regularity, surplus, records), which is squarely adviser territory, and the sequencing questions it raises are worked on the tax-free cash page and the withdrawal-order page.
Methodology. Spendable = £1,000 ÷ (1 − relief) × (1 − effective withdrawal tax); e.g. £1,000 ÷ 0.72 × 0.85 = £1,181, doubled by a full match to £2,361. Inheritance rows: pension pot £1,000 ÷ 0.6 = £1,667, × 0.6 IHT = £1,000 in-wrapper, then the heir's marginal rate; ISA £1,000 × 0.6 = £600. LSA ceiling £268,275 ÷ 0.25 = £1,073,100. PA remainder £12,570 − £12,548 = £22. Salary-sacrifice line £2,000 ÷ 5% + £6,240 = £46,240. All arithmetic machine-checked before publication. Published 8 August 2026 · figures last verified 8 August 2026.
Sonuswealth is pre-launch. The app is built to run this exact stack on real numbers: relief rate, match, salary sacrifice, allowance headroom, the £1,073,100 line and the April 2027 rules, per person, per household.