ISA vs GIA Calculator — Tax-Free vs Taxable Investing UK 2026
Compare a stocks and shares ISA with a General Investment Account side by side. See exactly how much capital gains tax and dividend tax erode your GIA returns — and how much extra an ISA saves you over 10 to 40 years.
Results
| ISA (Tax-Free) | GIA (Taxable) | |
|---|---|---|
| Total Invested | — | — |
| Gross Growth | — | — |
| CGT Paid | £0 | — |
| Dividend Tax Paid | £0 | — |
| Net Return | — | — |
| Final Value | — | — |
ISA vs GIA Final Value
How the ISA vs GIA Calculator Works
Enter your annual investment, how long you plan to invest, the expected return, your tax band, and the split between equities and bonds. The calculator projects year-by-year growth for both an ISA and a GIA, applying capital gains tax (20% above £3,000 exempt) and dividend tax (8.75% basic / 33.75% higher / 39.35% additional above £1,000 allowance) to the GIA only. The ISA grows completely tax-free.
Why ISAs Beat GIAs for Most UK Investors
The UK ISA is one of the most generous tax shelters in the world. A £20,000 annual allowance means a couple can shelter £40,000 per year completely free of capital gains tax, dividend tax, and income tax on returns. Over 20 years at 7% growth, the ISA advantage can exceed £50,000 compared to a GIA for a basic-rate taxpayer — and much more for higher-rate taxpayers. The key rule: always max out your ISA before investing in a GIA.
CGT and Dividend Tax Rules (2024/25)
Capital Gains Tax: 10% (basic rate) or 20% (higher/additional rate) on gains above the £3,000 annual exempt amount. Dividend Tax: 8.75% (basic), 33.75% (higher), 39.35% (additional) on dividends above the £1,000 dividend allowance. Both allowances apply per person per tax year. Transfers between spouses are exempt. Inside an ISA, none of these taxes apply.
Frequently Asked Questions
Should I use an ISA or a GIA?
Always max out your ISA allowance first — returns are completely tax-free (no CGT, no dividend tax, no income tax). Use a GIA only when you have exceeded the £20,000 annual ISA limit. The tax drag on a GIA can reduce your effective return by 1-2% per year depending on your tax band and asset allocation.
How much capital gains tax do I pay in a GIA?
In 2024/25, you pay 20% CGT on gains above the £3,000 annual exempt amount (higher/additional rate taxpayers). Basic rate taxpayers pay 10%. Shares in an ISA are exempt from CGT entirely.
What is the ISA annual allowance?
The ISA annual allowance is £20,000 per tax year (2024/25). You can split this across cash ISAs, stocks and shares ISAs, and innovative finance ISAs. Unused allowance does not roll over to the next year.