snapcalcs

ISA allowance calculator

Compare a tax-free ISA wrapper with a standard UK savings account and see exactly how much tax you'd save over your chosen time period. Works for cash, stocks & shares, and any other ISA type.

Tax band

Tax saved by using an ISA

£68

Over 10 years at 5.0% for a basic rate (20%) taxpayer

ISAStandard savings account
Initial investment£15,000£15,000
Returns after 10 years£9,433£9,365
Tax paid£0£66
Final value£24,433£24,365
Tax saved by using an ISA£68

That's £68 more in your pocket just from using the right wrapper — the same investment, the same return, but sheltered from UK income tax on interest and from capital gains tax on share growth.

ISA allowance for 2026/27

The annual ISA allowance for the 2026/27 tax year is £20,000 — unchanged since 2017 and frozen through at least the current parliament. You can split the £20,000 across any combination of ISA types:

Subscriptions reset on 6 April every year. Unused allowance does not carry forward — it's a "use it or lose it" deal. Since April 2024, you can subscribe to multiple ISAs of the same type within the same tax year, which was previously restricted to one per type.

Types of ISA

The right ISA depends on your timeframe and risk tolerance:

ISA typeBest forRisk
Cash ISAShort-term savings, emergency fund, near-term goalsLow (FSCS-protected to £85k per provider)
Stocks & shares ISA5+ year horizon, long-term wealth buildingMedium–high (market volatility)
Lifetime ISAFirst home purchase, or retirement at 60+Varies (cash or investments)
Innovative finance ISAP2P lending, higher-yield experienced saversHigh (no FSCS protection)

When an ISA makes the most difference

The tax saving from an ISA grows with three variables: your tax rate, the size of your balance, and the time you hold it.

Frequently asked questions

Yes. Since 6 April 2024, you can subscribe to multiple ISAs of the same type within a tax year — e.g. open two different cash ISAs with two different providers and split your contributions between them. The key rule hasn't changed: your total subscriptions across all ISAs in a tax year can't exceed the £20,000 annual allowance. A few exceptions apply: you can only subscribe to one Lifetime ISA per tax year (with a £4,000 cap inside the £20,000 total), and transfers between providers don't count as new subscriptions.