What an ISA saves you

Compare investing inside a Stocks and Shares ISA with a general account.

Your details

Your result

An ISA would leave you better off by£4,588
Value after 15 years
Stocks and Shares ISA£47,931
General account, after tax£43,344
Dividend tax paid along the way£720
Capital gains tax when you sell£3,726
Assumptions and limits

Assumes you use your £500 dividend and £3,000 gains allowances only on this investment and sell everything at the end, at today’s rates. You can put £20,000 a year into ISAs. Moving existing investments into an ISA (Bed and ISA) means selling first, which can trigger capital gains tax.

Sources: Individual Savings Accounts · Tax on dividends · Capital Gains Tax allowancesTax year 2026/27

Common questions

How much can I put in an ISA?

Up to £20,000 a year across all your ISAs. Unused allowance doesn’t carry over to the next tax year.

Why does an ISA make a bigger difference over time?

Dividend tax each year means less is reinvested, and capital gains tax is due when you sell. In an ISA, neither applies, so more of your money keeps growing.

How we calculate

Every calculator uses the published 2026/27 rates from one shared set of rules, so when a rate changes, it changes everywhere.

Where rates come from

Tax, National Insurance, student loan, benefit and property tax rates come from GOV.UK. Each calculator links to its sources.

What we don’t cover

Scottish income tax bands, tax codes other than 1257L, benefits in kind and your personal circumstances. Results are estimates to help you plan, not a payslip or advice.