Answers · UK 2025/26
What happens if I go over my ISA allowance?
If you exceed the £20,000 ISA allowance for 2026/27, HMRC will usually spot it and instruct your provider to remove the excess, including any interest or growth on it, which becomes taxable. You should not try to fix it yourself — wait for HMRC and avoid repeating the mistake.
Full answer
The ISA allowance is £20,000 for 2026/27 across all your ISAs combined (cash, stocks and shares, innovative finance and Lifetime ISA, with the LISA capped at £4,000). If you accidentally pay in more than £20,000, the excess subscription is invalid. HMRC reconciles ISA data after the tax year and will typically write to you and tell your provider to remove the over-subscribed amount; any interest, dividends or growth attributable to the excess loses its tax-free status and is treated as taxable income or gains. Worked example: you pay £22,000 into ISAs in one year. The extra £2,000 is invalid; HMRC has it removed, and any interest earned on that £2,000 becomes taxable at your marginal rate. Importantly, do not withdraw money yourself before HMRC contacts you, as you could make things worse — HMRC's guidance is to wait for instructions. There is normally no penalty for an honest first mistake. To avoid it, track contributions carefully, remember the single combined limit, and note that flexible ISAs let you replace withdrawals within the same tax year without using fresh allowance. Use the Savings calculator to plan contributions within your allowance.
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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.