Stocks & Shares ISA Calculator (UK)
Tax-free ISA growth — £20,000 annual allowance, monthly contributions and the compounding shelter explained.
Formula
Disclaimer: Assumes constant returns; market investments fluctuate and tax rules change — verify current-year limits. Educational math only, not financial or tax advice.
Need stocks & shares isa calculator results fast? Skip the spreadsheet and get a clear, defensible answer in one step — free, private and instant, recalculating live as you change any input.
About Stocks & Shares ISA Calculator (UK)
The Stocks & Shares ISA is the UK's cleanest wealth wrapper: £20,000 of new money per tax year, inside which dividends, interest and capital gains are permanently tax-free and never even appear on a tax return. The default £500/month at 7% builds about £260,000 over 20 years — roughly £140,000 of it growth that a taxable account would have shared with HMRC. The shelter's value has grown as allowances elsewhere shrank: the CGT annual exempt amount and dividend allowance have both been cut hard, so even modest portfolios now generate tax outside wrappers. ISA money also stays accessible (no pension-style lock), making it the natural home for every pound after the employer-match pension contribution is captured. Allowance discipline: it's use-it-or-lose-it each tax year (no carry-forward), the £20,000 spans all ISA types you fund that year, and 'flexible' ISAs let you withdraw and replace within the same year without burning allowance — check your provider's flag. Couples plan per-person: £40,000 of household shelter annually, and Junior ISAs add more per child.
How to use Stocks & Shares ISA Calculator (UK)
- 1Enter Monthly contribution, Expected annual return (%), Period (years) into the Stocks & Shares ISA Calculator.
- 2The result is computed automatically using Standard monthly compounding — with zero tax on dividends, interest or capital gains inside the wrapper — there is no button to press; it updates live as you type.
- 3Change any input to model a different scenario, then use “Copy result link” to share the exact numbers.
Why use Stocks & Shares ISA Calculator (UK)?
- ✓Computes stocks & shares isa calculator instantly with the correct formula — no spreadsheet needed
- ✓100% free and unlimited, with no sign-up, login or paywall
- ✓Runs entirely in your browser, so the figures you enter are never uploaded or stored
- ✓Shows the formula, a live worked example and references so you can defend the number
Frequently asked questions
Is ISA growth really completely tax-free?+
Yes — no capital gains tax, no dividend tax, no further income tax, no reporting, regardless of how large the pot grows. Famous 'ISA millionaires' pay nothing on withdrawals. The only taxes that ever touch ISAs are inheritance-tax interactions on death (spousal transfers are protected via the additional permitted subscription).
Cash ISA or Stocks & Shares ISA?+
Horizon decides: under ~5 years, cash ISA (capital certainty); beyond, equities have historically beaten cash decisively and the tax shelter amplifies the difference. Many split — emergency buffer in cash ISA, long-term money in S&S. The £20,000 allowance is shared across whatever mix you choose.
What happens if I exceed the £20,000 allowance?+
HMRC repairs it — excess subscriptions get removed/voided with any growth taxable, usually after a letter rather than a fine for honest errors. Providers now block most over-subscriptions at deposit. If you've paid into ISAs at two providers and breached, call HMRC's ISA helpline before acting; don't self-fix by withdrawing.
Can I move old ISAs without losing the wrapper?+
Yes — via formal ISA TRANSFER (the new provider pulls the funds); never withdraw-and-redeposit, which burns allowance. Old-year money transfers without limit and doesn't touch this year's £20,000. Transferring to cheaper platforms is one of the highest-value admin hours in UK investing — fee drag compounds exactly like returns.
Related Finance tools
Human Life Value (HLV) Calculator
The economic value of your future earnings to your family — the income-replacement basis for sizing a life-insurance cover.
● LiveTerm Life Insurance Coverage Calculator
How much term-life cover you actually need — replacing income, clearing debts and funding goals, net of existing assets and cover.
● LiveDIME Method Life Insurance Calculator
The DIME formula — Debt + Income + Mortgage + Education — a fast, complete way to size a life-insurance cover.
● Live