ISA Calculator UK 2026

Compare Cash ISA, Stocks & Shares ISA, and Lifetime ISA. See how your money grows tax-free with annual contributions and government bonuses.

ISAs are the most tax-efficient way for UK residents to save and invest. You can shelter up to £20,000 per year from income tax and capital gains tax. HMRC data shows that UK adults held over £700 billion in ISAs in 2024/25, yet many people fail to use their full annual allowance and miss out on years of tax-free growth.

There are three main types: Cash ISAs offer guaranteed returns with no risk, Stocks and Shares ISAs offer higher potential returns with market risk, and the Lifetime ISA adds a 25% government bonus (up to £1,000 per year) for first-time buyers or retirement savings.

This calculator compares all three side by side. Enter your planned annual contribution, expected returns, and time horizon to see projected values, tax savings, and government bonuses.

How it works

  1. Enter your annual ISA contribution and choose the ISA types to compare.
  2. Set expected interest rates or investment returns for each type.
  3. View projected values over your chosen time horizon with tax savings and bonus calculations.

Written by the CalcStack team

Figures for the 2026/27 UK tax yearlast verified Sources: GOV.UK Individual Savings Accounts, GOV.UK Lifetime ISA

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Frequently asked questions

What is an ISA?▾
An Individual Savings Account (ISA) is a tax-free wrapper for your savings or investments. You pay no income tax or capital gains tax on the money you earn in an ISA. The annual allowance for 2025/26 is £20,000 across all ISA types.
What is the difference between Cash ISA and Stocks & Shares ISA?▾
A Cash ISA works like a savings account with a fixed or variable interest rate. A Stocks & Shares ISA invests your money in funds, shares, or bonds with potentially higher returns but more risk — your capital can go down as well as up.
What is a Lifetime ISA?▾
A Lifetime ISA (LISA) is available to 18-39 year olds. You can save up to £4,000 per year and the government adds a 25% bonus (up to £1,000/year). You can use it for your first home (up to £450,000) or retirement (after age 60).
What is the LISA penalty for early withdrawal?▾
If you withdraw from a LISA for anything other than buying your first home or after age 60, you pay a 25% penalty on the withdrawal. This effectively means you lose the government bonus plus some of your own money.
How much can I put in an ISA each year?▾
The total ISA allowance for 2025/26 is £20,000. You can split this across different ISA types (Cash, Stocks & Shares, Innovative Finance, Lifetime), but the LISA has its own sub-limit of £4,000 which counts towards the £20,000 total.
Can I transfer between ISA types?▾
Yes, you can transfer ISAs between providers and between types (e.g., Cash to Stocks & Shares). Transfers do not count against your annual allowance. Always use the official transfer process rather than withdrawing and re-depositing.
Are ISA returns guaranteed?▾
Cash ISA rates are usually fixed or variable but your capital is safe (protected by FSCS up to £85,000). Stocks & Shares ISA returns are not guaranteed — investments can go down as well as up.
What happens to my ISA when I die?▾
Your ISA loses its tax-free status on death, but your spouse or civil partner receives an Additional Permitted Subscription (APS) equal to the value of your ISA, allowing them to shelter the same amount in their own ISA.
Should I max out my ISA?▾
If you have spare funds after building an emergency fund and paying off high-interest debt, using your ISA allowance is one of the best ways to grow your wealth tax-free. Even small regular contributions benefit from compound growth.
What is the best ISA for me?▾
For short-term savings (1-3 years), a Cash ISA provides security. For long-term goals (5+ years), a Stocks & Shares ISA historically provides better returns. A LISA is excellent if you are saving for a first home or additional retirement savings.

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