ISA Calculator
Calculate tax-free ISA growth with Cash ISA, Stocks & Shares ISA, or Lifetime ISA (LISA) with 25% bonus.
Max £1,667/month for £20k annual allowance
Cash ISA: 4-5% | S&S ISA: 6-8% avg
Final ISA Value
£93k
Total Contributions
£65,000
Tax Saved
£0
Investment Growth
£27,784
Total Return
42.7%
Tax-Free Benefits
All growth is completely tax-free. No income tax on dividends or interest, no capital gains tax on profits.
ISA Growth Projection
Assumes 6% annual return. Past performance is not indicative of future results. Not financial advice.
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How to Use the ISA Calculator
Our free ISA calculator shows how much your tax-free savings could grow over time. Enter your initial deposit, monthly contributions, expected annual return, and investment period to see your projected final ISA value, total contributions, and tax-free growth.
Toggle the Lifetime ISA (LISA) option to see how the 25% government bonus affects your savings, ideal for first-time buyers or those saving for retirement aged 60+.
ISA Allowance 2026/27: What You Need to Know
Every UK adult can save or invest up to £20,000 per tax year across all ISAs, completely free from Income Tax and Capital Gains Tax. This is the ISA allowance, and it resets every 6 April. Unused allowance cannot be carried forward.
Annual ISA Allowance
£20,000
LISA Maximum
£4,000/yr
LISA Bonus
25%
Junior ISA Allowance
£9,000/yr
Types of ISA Explained
Cash ISA
Works like a standard savings account but with no tax on interest. Best for short-term savings or those close to retirement. Current rates: 4–5% AER from leading providers.
Ideal for: Risk-averse savers, emergency funds, short-term goals
Stocks & Shares ISA
Invest in shares, funds, bonds, and ETFs tax-free. Historically delivers 6–8% average annual returns over 10+ years, but the value can fall as well as rise.
Ideal for: Long-term investors (5+ year horizon), building wealth for retirement
Lifetime ISA (LISA)
Save up to £4,000/year and receive a 25% government bonus (up to £1,000/year). Use for a first home (worth up to £450,000) or retirement (aged 60+). A 25% withdrawal penalty applies for other uses.
Ideal for: First-time buyers or those saving for retirement aged 60+
Innovative Finance ISA
Invest in peer-to-peer lending platforms tax-free. Higher potential returns than cash (5–10%), but higher risk, not covered by FSCS protection.
Ideal for: Experienced investors comfortable with higher risk
Cash ISA vs Savings Account: Which is Better?
For basic rate taxpayers, the Personal Savings Allowance (PSA) allows up to £1,000 of interest tax-free (£500 for higher rate taxpayers). If your savings interest stays below this, a regular savings account with a competitive rate may offer similar returns without needing an ISA.
However, as your savings grow or interest rates rise, the PSA is easily exceeded, at which point an ISA wrapper becomes increasingly valuable. For Stocks & Shares ISAs, Capital Gains Tax (up to 18–24%) and dividend tax savings can be significant for larger portfolios.
💡 Rule of thumb
If you have more than £20,000–£25,000 in savings, or plan to invest long-term, an ISA is almost always the most tax-efficient vehicle available to UK savers.
Best Cash ISA Rates in 2026
With the Bank of England base rate having been cut from its 2023 peak, Cash ISA rates are still competitive. Top providers as of October 2026 are offering:
Easy Access Cash ISA
Up to 4.80% AER
Flexible, withdraw anytime
2-Year Fixed Cash ISA
Up to 5.08% AER
Tandem, locked in for 2 years
5-Year Fixed Cash ISA
Up to 5.25% AER
Shawbrook, locked in for 5 years
*Rates indicative only. Always check MoneySavingExpert or the provider directly for current best-buy rates.
The Power of Starting Early: ISA Growth Examples
Compound growth means that time in the market is more powerful than timing the market. Here's what saving £500/month into a Stocks & Shares ISA at 7% average annual return could look like:
5 years
~£35,800
You put in £30,000
Growth: +19%
10 years
~£87,000
You put in £60,000
Growth: +45%
20 years
~£262,000
You put in £120,000
Growth: +118%
30 years
~£607,000
You put in £180,000
Growth: +237%
*Illustrative only. Assumes 7% average annual return (Stocks & Shares ISA). Past performance is not a guide to future returns. Capital at risk.
⚠️ Important Disclaimer
This ISA calculator is for illustrative purposes only and does not constitute financial advice. Investment returns are not guaranteed and the value of your ISA can fall as well as rise. Past performance is not indicative of future results. ISA rules may change in future tax years. Always read the key investor information and consider seeking advice from an FCA-authorised financial adviser before investing. Data last verified July 2026.
Worked Example: £10,000 in a Stocks and Shares ISA
If £10,000 grows at an average 5% a year for ten years, it becomes about £16,289. The £6,289 gain sits inside the ISA, so there is no Capital Gains Tax or tax on dividends. Held outside an ISA, the same gain could use up your annual exempt amount and be taxed above it.
Frequently Asked Questions
Can I have more than one ISA?
Yes. You can pay into several ISAs in the same tax year, as long as the total stays within your overall annual allowance.
Can I take money out and put it back?
Only with a flexible ISA. Otherwise money you withdraw has used up that part of your allowance for the year.
What is a Lifetime ISA?
It is for a first home or retirement from age 60. You can save up to £4,000 a year and get a 25% government bonus, with penalties for other withdrawals.
Frequently Asked Questions
What is an ISA?
An Individual Savings Account (ISA) lets you save or invest tax-free. No income tax or capital gains tax on returns. UK residents only.
What is the ISA allowance?
£20,000 per tax year (2026/27). You can split this across Cash ISA, Stocks & Shares ISA, Innovative Finance ISA, and Lifetime ISA.
What is a Lifetime ISA (LISA)?
LISA gives 25% government bonus on up to £4,000/year. For first-time homes (£450k max) or retirement (age 60+). 25% penalty for other withdrawals.
Cash ISA or Stocks & Shares ISA?
Cash ISA: safe, fixed/variable interest. Stocks & Shares ISA: invested in markets, higher potential returns but risk of losses. Depends on timeframe and risk tolerance.
Can I use this as a Cash ISA calculator?
Yes, set your expected annual return to a typical Cash ISA rate (around 4-5%) and leave the Lifetime ISA option unchecked to see exactly how much tax-free interest a Cash ISA would earn.
Key Terms Explained
Plain-English definitions of the financial terms used in this calculator.
- AER (Annual Equivalent Rate)
- The interest rate on savings accounts once compounding is included, showing what you would actually earn over a year. Use AER, not the headline gross rate, to compare savings accounts fairly.
- Compound Interest
- Interest earned on both your original money and on interest already added. Over long periods compounding accelerates growth dramatically, the earlier you start saving or investing, the more it works in your favour.
- ISA (Individual Savings Account)
- A UK account where interest, dividends and capital gains are completely tax-free. You can pay in up to £20,000 per tax year across Cash ISAs, Stocks & Shares ISAs and Lifetime ISAs.
- Dividend
- A share of company profits paid to shareholders. UK taxpayers get a tax-free dividend allowance each year; dividends above it are taxed at lower rates than salary income.
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Not Financial Advice: This calculator is for informational and educational purposes only. Results are estimates and do not constitute financial advice, recommendations, or regulated advice. We are not authorised or regulated by the Financial Conduct Authority (FCA). Always consult a qualified financial adviser for personalised advice. Tax treatment depends on your individual circumstances and may change. Tax laws and rates may change. Past performance does not guarantee future results.
