About the ISA Allowance Calculator
Every UK tax year (6 April to 5 April) you get one combined ISA allowance to split across Cash, Stocks & Shares, Innovative Finance and Lifetime ISAs however you like. Once the tax year ends, any unused allowance is lost — it doesn't carry forward. This calculator shows how much of your allowance you have left based on what you've already contributed.
How it works
Remaining allowance = £20,000 − total contributed across all your ISAs this tax year
The £20,000 limit is shared across every ISA type you hold — contributing £12,000 to a Cash ISA leaves only £8,000 of headroom for a Stocks & Shares ISA in the same tax year, for example.
Assumptions and behaviour
- Uses the 2026/27 annual ISA allowance of £20,000 (the Junior ISA limit is separate, at £9,000, and not covered here).
- Assumes contributions entered are the total across all ISA types combined for the current tax year.
- Doesn't distinguish between ISA types — the £20,000 limit applies to your combined total, not per account.
Limitations
- Doesn't check Lifetime ISA's own £4,000 sub-limit (part of, not additional to, the overall £20,000).
- Doesn't account for withdrawals and flexible ISA rules, which some providers let you replace within the same tax year without it counting against your allowance again.
- Estimates only — not financial advice.
Privacy
The calculation runs entirely in your browser. Nothing is uploaded or stored.
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