A Stocks & Shares ISA is a tax-free wrapper for your investments. Any dividends, interest, and capital gains generated inside the ISA are completely free from UK tax — forever. No reporting, no allowances to worry about, no tax returns. This guide explains why it matters and how to make the most of it.
What is tax-free inside an ISA?
- Dividends: no dividend tax (outside an ISA: 8.75%–39.35%)
- Capital gains: no CGT on selling investments (outside: 18%–24%)
- Interest: no income tax on bond interest or cash holdings
There is no tax to pay when you withdraw money from an ISA, and ISA income does not count towards your income for any other tax calculation.
The annual allowance
You can invest up to £20,000 per tax year across all ISA types (Cash ISA, Stocks & Shares ISA, LISA, Innovative Finance ISA). Unused allowance cannot be carried forward — use it or lose it.
ISA vs general investment account (GIA)
Outside an ISA, you face:
- Dividend Allowance: only £500 tax-free, then 8.75%–39.35%
- Capital Gains: only £3,000 exempt, then 18%–24%
- Interest: Personal Savings Allowance of £1,000/£500 only
For long-term investors, the compounding effect of tax-free growth is enormous. A £20,000 investment growing at 7% over 20 years produces approximately £77,000 in an ISA vs. ~£60,000 in a GIA (after CGT on disposal).
Flexible ISAs
Some ISA providers offer "flexible" ISAs — if you withdraw money, you can replace it within the same tax year without it counting towards your £20,000 allowance. Not all providers offer this, so check before withdrawing.
Transferring ISAs
You can transfer ISAs between providers without losing the tax-free status. Always use the formal transfer process — withdrawing and re-investing uses up new allowance.
ISAs and your wider tax position
ISA income does not appear on your tax return and does not affect your Personal Allowance, Child Benefit charge, or pension taper. Use the income tax calculator to understand your non-ISA income position and see how much headroom you have in each tax band.