ISA vs Pension Calculator — Compare Tax Benefits Side by Side — UK 2026

ISA Calculator UK

Understanding Your Investment Returns

This calculator projects your returns using compound interest, where your earnings generate their own earnings over time. The power of compounding means that even small regular investments can grow into substantial wealth over long periods. For example, investing just Rs 5,000 per month at 12% expected returns for 25 years can grow to over Rs 1 crore — of which only Rs 15 lakh is your own money and Rs 85 lakh is compounding returns. The key factors that determine your final corpus are: the amount invested, the rate of return, the duration of investment, and the frequency of compounding.

Important Considerations

Past returns do not guarantee future performance, especially for market-linked instruments like mutual funds and equities. The returns shown are estimates based on the rate you enter. Equity investments carry market risk but have historically delivered 12-15% CAGR over 15+ year periods in India. Fixed income options like PPF (7.1%) and FD (6-7.5%) offer lower but more predictable returns. Diversifying across asset classes — equity, debt, gold, and real estate — reduces overall portfolio risk while optimizing returns for your risk tolerance.

ISA vs Pension — The Maths That Decides It

A pension beats an ISA on the way in because of tax relief: getting £100 into a pension costs a basic-rate taxpayer £80, a higher-rate taxpayer £60 and an additional-rate taxpayer £55, while £100 into an ISA always costs £100. The ISA wins on the way out: withdrawals are tax-free at any age, whereas pension money is locked until age 55 (rising to 57 on 6 April 2028) and — beyond the 25% tax-free lump sum, capped at £268,275 per current legislation — is taxed as income. Run the numbers on £10,000 of gross salary saved each year for 20 years at 5% annual growth. The pension receives the full £10,000 a year and compounds to roughly £330,700. A basic-rate taxpayer can only put £8,000 a year into an ISA after tax, reaching about £264,500 — all accessible tax-free. Drawing the pension as 25% tax-free cash with the rest taxed at 20% leaves about £281,100 net, so the pension finishes 6.25% ahead. For a higher-rate taxpayer the gap is dramatic: £6,000 a year in the ISA grows to about £198,400, while the same £330,700 pension pot drawn at basic rate nets around £281,100 — 41.7% more. The frozen £12,570 personal allowance usually widens the pension's lead further, because the first slice of retirement income can be drawn tax-free.

When ISA Beats Pension

The ISA wins in four situations. First, timing: pension money is inaccessible until 55, rising to 57 from 6 April 2028, so any goal before then — a house deposit, a career break, bridging early retirement — belongs in an ISA. Second, tax-band inversion: if you only receive 20% relief now but expect retirement income above the higher-rate threshold (£50,270, frozen per current legislation), the pension's entry advantage can be clawed back on exit. Third, very large pots. The £1,073,100 lifetime allowance was abolished on 6 April 2024 under the Finance Act 2024 and replaced by a £268,275 lump sum allowance, removing the old tax charge on seven-figure pensions — but reinstatement has been floated politically, and savers near the old limit often hedge by directing new money to ISAs instead. Fourth, inheritance. The October 2024 Budget announced that unused pension funds are due to come within inheritance tax from 6 April 2027 (per current legislation), eroding what was previously the pension's biggest estate-planning edge; ISAs have always sat inside the estate, taxed at 40% above the £325,000 nil-rate band (plus £175,000 residence band). One more trap: flexibly accessing taxable pension money triggers the £10,000 money purchase annual allowance on future contributions, while a flexible ISA lets you withdraw and replace cash in the same tax year without penalty.

Stocks and Shares ISA vs Pension Pot — Same Investments, Different Wrappers

A stocks and shares ISA and a pension can hold identical investments — the same global index fund, investment trust or bond ETF grows at exactly the same pre-tax rate in either. Neither wrapper charges capital gains or dividend tax internally (outside a wrapper you would get only a £3,000 CGT exemption and £500 dividend allowance as of 2026). What differs is limits, access and exit tax. The ISA allowance is £20,000 per tax year and has been frozen since 2017/18. The pension annual allowance is £60,000 — raised from £40,000 in April 2023 — and unused allowance from the three previous tax years can be carried forward, giving a potential £240,000 of contributions in the 2026/27 tax year. Two caps apply: tax-relieved contributions cannot exceed 100% of relevant earnings, and the allowance tapers to as little as £10,000 once adjusted income passes £260,000. The pension's genuinely unbeatable feature is the employer match. Under auto-enrolment (Pensions Act 2008), employers must pay at least 3% of qualifying earnings within the 8% minimum, and many match well beyond that. A matched contribution is an instant 100% return before any market growth: £100 of matched pension saving costs a higher-rate taxpayer £60 and buys £200 of pot. No ISA, whatever its flexibility, can replicate that arithmetic — which is why almost every adviser says take the full match before funding an ISA.