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Investing · £20k ISA limit

ISA vs GIA Tax Calculator

ISAs shelter dividends and capital gains entirely. Outside an ISA (in a General Investment Account), dividends and gains above tiny allowances are taxed. Compare the bill.

£
%
%
yrs

Tax saved by using an ISA

£11,045

Dividend tax (GIA, 10y)£4219
CGT on realised gain£6827
Total GIA tax£11045

How we calculated your result

Dividend allowance is £500. Above that, dividends taxed at 8.75% (basic), 33.75% (higher), 39.35% (additional). Capital gains: £3,000 AEA, then 18% / 24%. ISA pays zero on both.

Official UK rules in simple English

  • ISA subscription limit £20,000 (2025/26).
  • Dividend allowance £500 in a GIA.
  • CGT AEA £3,000.
  • No annual reporting needed for ISAs.

Common pitfalls to watch out for

  • ⚠ Fill ISA first, every year

    You can’t backdate. Unused allowance disappears every 5 April.

  • ⚠ Bed & ISA for existing GIA holdings

    Sell GIA → buy back inside ISA. Crystallises gain (within AEA) but shelters future growth.

  • ⚠ Flexible vs non-flexible ISA

    A flexible ISA lets you withdraw and replace in the same year. Non-flexible doesn’t — withdrawal eats your annual allowance.

Frequently asked questions

What about Lifetime ISA?
Separate £4k allowance with 25% gov bonus — for first home or age 60+.
Can I have multiple ISAs?
Yes — from April 2024 you can subscribe to multiple ISAs of the same type in one year.

Educational. ISA rules change frequently — confirm current limits before subscribing.

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