How it works
How ISA Allowance Calculator (UK) solves the problem
Use this ISA Allowance Calculator (UK) when you need a ISA allowance calculator UK you can trust — clean inputs, transparent steps, zero fluff.
ISA Allowance Calculator (UK) takes the same method a textbook or spec sheet would recommend and wraps it in a widget — you get the answer, the formula and a sense of when the number breaks down.
Run the net number, not the headline rate: that is where surprises hide. Put the real cash figures in, even if they are rough — then run the sums and the rest of this page explains what the answer means.
The annual ISA subscription limit is £20,000 (2024/25 onwards unless changed in Budget). You can split it across Cash ISA, Stocks & Shares ISA, Lifetime ISA (max £4,000 LISA sub-limit) and Innovative Finance ISA. Unused allowance does not roll over.
On this page you will see tax, Personal Finance and GOV.UK treated as first-class terms — each one is linked to the calculators and references that use it, so you can follow the thread without retyping queries into a search bar.
If it helps, jump straight to the Finance hub or compare with the Compound Interest Calculator and the Pension Contribution Calculator — those two calcs are the ones readers usually open right after this page.
Seeing it on real numbers
A working example keeps the formula honest:
A saver maxes out £4,000 into a Lifetime ISA (earning the 25% government bonus = £1,000), then splits the remaining £16,000 between a Stocks & Shares ISA (£12,000) and a Cash ISA (£4,000). Nothing goes into an Innovative Finance ISA. Total subscribed: £20,000; total pot credited that year (with LISA bonus): £21,000.
A first-time buyer on their 40th birthday realises they can no longer open a new LISA (age 40 cap) but can still contribute to an existing one until 50. If they opened a LISA at 39 with £1, they preserve the ability to add £4,000/year for another decade — £4,000 × 10 = £40,000 plus £10,000 bonus, all tax-free and compliant with the £450,000 property-price cap.
When to use this calculadora
ISA Allowance Calculator (UK) is aimed at people arriving with questions like these:
- "ISA allowance 2026"
- "Stocks and shares ISA limit"
- "Cash ISA limit UK"
- "ISA subscription limit"
- "How much can I put in ISA"
- "What is isa allowance calculator uk"
When to reach for something else
Every tool has an edge where it stops being the right answer. ISA Allowance Calculator (UK) is no exception:
- For legally binding tax or medical decisions — cross-check with HMRC, NHS or a qualified professional.
- For very large or very small extremes the rounding error outgrows the useful precision.
- When the underlying rate or threshold has changed since the page was last reviewed — always verify with the primary source.
- When the input you have is already a derived figure (net of something) — feeding it in as "gross" will double-subtract.
What goes wrong nine times out of ten
Every time you run the sums for a new scenario, one of these creeps in — it's worth knowing them ahead of time.
- Opening more than one of the same ISA type in the same tax year (new rules from April 2024 allowed multiple of the same type, but many providers still reject mid-year transfers).
- Assuming the LISA 25% bonus is free money — it is, unless you withdraw for a non-qualifying reason, in which case the 25% penalty on withdrawals means you get back less than you put in.
- Running down an old ISA and rushing to replace the cash within the tax year. Withdrawing then re-depositing normally counts twice against the £20,000 unless the ISA is a Flexible ISA.
- Exceeding the LISA £4,000 sub-cap and expecting the excess to spill into your Stocks & Shares ISA. HMRC treats excess LISA contributions as unauthorised — the provider refuses them.
The sources behind the numbers
Where the maths needs an external authority, we cross-check against:
- GOV.UK
- HMRC
- FCA
Works well alongside
If this question keeps coming up for you, the same cluster of tools usually comes next:
- Compound Interest Calculator — Project the future value of savings or investments with compounding, regular contributions and inflation-adjusted returns.
- Pension Contribution Calculator — See how salary sacrifice and employer matching affect your take-home pay and pension pot.
- Dividend Tax Calculator (UK) — Work out income tax on dividends above the Dividend Allowance at basic, higher and additional rates — including typical director/shareholder scenarios for UK limited companies.
- Capital Gains Tax Estimator (UK) — Estimate CGT on shares, funds or other chargeable assets using the annual exempt amount and the correct rate band for your income — residential property uses different rates than other assets.
How we keep this accurate
Our calculadoras run on pure, unit-tested functions — the same logic lives in the browser and in the CI test suite. When tax rates, thresholds or official figures move, the update lands within 24 hours of the announcement. You can read the editorial policy and corrections policy.
Found an out-of-date number on ISA Allowance Calculator (UK) or anywhere else in the Finance toolkit? Send it to the editorial desk and we'll patch it. Or browse the full calculadora directory for the next tool you need.
