ISA Calculator UK 2025/26
Project how your ISA savings will grow with compound interest or investment returns. Choose your ISA type, enter your contributions and see your projected pot — including the government bonus for Lifetime ISA holders.
Choose your ISA type and enter your contributions, then click Calculate to see your projected growth.
What is an ISA?
An Individual Savings Account (ISA) is a UK savings and investment wrapper that shelters your money from income tax and capital gains tax. Any interest, dividends or growth earned inside an ISA is completely tax-free — you never pay tax on it when you withdraw, and you do not need to declare it on a self-assessment tax return. For 2025/26, every UK adult can save or invest up to £20,000 per year across all their ISAs combined.
ISAs were introduced in 1999 and have become one of the most important long-term savings tools available to UK residents. Over time, the power of tax-free compound growth means that consistent ISA savers can accumulate substantial wealth that is entirely sheltered from HMRC — especially when starting early.
Types of ISA in the UK
There are four main types of ISA available in 2025/26:
- Cash ISA — Works like a standard savings account, but all interest earned is tax-free. Available as easy-access or fixed-rate. Best for short-term savings or emergency funds. Annual allowance: £20,000.
- Stocks & Shares ISA — Invest in funds, shares, bonds and ETFs with all gains and income completely tax-free. Higher long-term growth potential than Cash ISAs, but with investment risk. Annual allowance: £20,000.
- Lifetime ISA (LISA) — Available to those aged 18–39. Save up to £4,000 per year and receive a 25% government bonus (up to £1,000/yr). Can be used to buy a first home (property up to £450,000) or accessed tax-free at age 60+. A 25% withdrawal charge applies for any other use.
- Junior ISA (JISA) — For children under 18. Parents or guardians can save up to £9,000 per year. Funds are locked until the child turns 18, when the Junior ISA automatically converts to an adult ISA.
How Does the £20,000 ISA Allowance Work?
The £20,000 annual ISA allowance is the maximum you can pay into ISAs in a single tax year (6 April to 5 April). Since April 2024, the rules were relaxed to allow you to subscribe to multiple ISAs of the same type in the same year. You can now split the allowance across as many providers as you like — for example, £5,000 into one Cash ISA and £15,000 into a Stocks & Shares ISA — as long as the total does not exceed £20,000.
The LISA's £4,000 annual contribution limit counts towards the £20,000 overall allowance. If you put the maximum £4,000 into a LISA, you have £16,000 remaining for other ISAs. The Junior ISA allowance (£9,000) is entirely separate and does not eat into the adult £20,000. Unused ISA allowance cannot be carried forward — if you don't use it in the tax year, it is lost.
Cash ISA vs Stocks & Shares ISA
The right ISA type depends on your time horizon and attitude to risk. Cash ISAs offer certainty — your capital is protected, FSCS-guaranteed up to £85,000 per provider, and you earn a predictable interest rate. They suit money you may need within the next three to five years, or for holding your emergency fund. In 2025, competitive easy-access Cash ISA rates sit around 4–5%.
Stocks & Shares ISAs have historically delivered significantly higher returns over the long term. The FTSE All-World index has returned around 7–8% per year on average over the past 30 years, though with considerable short-term volatility. Over a 20+ year horizon, the compounding effect of higher returns can produce an ISA pot that dwarfs what a Cash ISA would achieve — though past performance is no guarantee of future results and the value of investments can fall as well as rise.
Frequently Asked Questions
How much can I put in an ISA in 2025/26?
The annual ISA allowance for 2025/26 is £20,000 per person. This can be spread across multiple ISA types — Cash, Stocks & Shares and Innovative Finance — as long as the combined total does not exceed £20,000. The Lifetime ISA has a sub-limit of £4,000 per year, which counts towards the overall £20,000. If you have a child, you can also save up to £9,000 per year into a Junior ISA, completely separately from the adult limit.
Is ISA interest tax-free?
Yes — all interest, dividends and capital gains earned within an ISA are completely free from UK income tax and capital gains tax. You do not need to declare ISA income or gains on a self-assessment tax return. This tax-free status is one of the biggest advantages of ISAs: over many years, avoiding tax on reinvested returns can dramatically increase your final pot through the power of tax-free compounding.
What is a Lifetime ISA and who qualifies?
A Lifetime ISA (LISA) is available to UK residents aged 18–39. You can save up to £4,000 per year and the government adds a 25% bonus (up to £1,000/yr) paid directly into your LISA. The LISA can only be used without penalty for two purposes: buying your first home (property price up to £450,000) or withdrawing from age 60 for retirement. Any other withdrawal incurs a 25% government charge, which claws back the bonus and a portion of your own savings. You must open a LISA before your 40th birthday, though you can continue contributing until age 50.
Can I have multiple ISAs in the same tax year?
Yes. Since April 2024, the rules were relaxed to allow you to subscribe to multiple ISAs of the same type in the same tax year. Previously, you could only open and pay into one of each type per year. You can now split your £20,000 allowance across as many Cash ISAs, Stocks & Shares ISAs and other eligible ISAs as you like, in any combination, provided the annual total does not exceed £20,000. This makes it easier to chase the best rates across multiple providers.
What happens if I exceed my ISA allowance?
If you pay more than £20,000 into ISAs in a single tax year, HMRC will contact you. The excess amount is not ISA-protected and any interest or gains it earned inside the ISA may be subject to tax. Most ISA providers alert you when you approach the limit, and many block further contributions once the allowance is used. If you hold ISAs with multiple providers, it is your responsibility to track your total subscriptions for the year to avoid a breach.