Answers · UK 2025/26
What happens if I do not use my ISA allowance by 5 April?
Unused ISA allowance is lost at end of tax year (5 April) — you cannot carry forward. The £20,000 resets fresh on 6 April. ISA allowances are use-it-or-lose-it, unlike pension Annual Allowance which carries forward 3 years.
Full answer
UK ISA allowance end-of-year rules 2025/26. Annual allowance: £20,000 per person per tax year (6 April to 5 April). Lifetime ISA sub-limit: £4,000/year within £20,000. Junior ISA: £9,000/year separately. Use it or lose it: any unused allowance is GONE at 5 April. No carry-forward (unlike pensions, which allow 3-year carry-forward of unused Annual Allowance up to £180,000+ extra). Action before 5 April: fund as much as possible — even a small contribution preserves future tax-free growth. Compound effect example: £20,000 invested for 20 years at 5% real return = ~£53,000. Skip a year = miss that £53,000. Multi-year impact: in 20 years of saving, missing one £20,000 allowance reduces wealth by ~£53,000 (assuming you saved it elsewhere subject to tax). Practical tactics. (1) Set up monthly direct debits early in the year so you don't scramble in March. (2) "Bed and ISA": sell taxable investments + immediately rebuy inside ISA — uses allowance, crystallises gain (within £3,000 CGT exempt). (3) If you can't afford full £20,000, prioritise: emergency fund in Cash ISA → LISA (if under 40) for property/retirement → S&S ISA for long-term. From April 2024 multiple-ISA contribution rule means you can split across providers within the year. Junior ISA: same end-date — easy to forget. The 5 April rush often causes platform/website delays — don't leave to last day.
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This answer is informational only and does not constitute financial, tax or legal advice. Figures are for the 2025/26 UK tax year. See our methodology and sources.