Answers · UK 2025/26
Can you backdate ISA contributions to a previous tax year?
No. ISA contributions cannot be backdated. Each tax year's £20,000 allowance runs from 6 April to 5 April and cannot be carried forward or backdated.
Full answer
The annual ISA allowance is a use-it-or-lose-it allowance. In 2026/27, you can subscribe up to £20,000 in total across all your ISAs (Cash ISA, Stocks and Shares ISA, Innovative Finance ISA, and Lifetime ISA combined). Any unused allowance from a previous tax year is permanently lost -- you cannot carry it forward or retroactively attribute a current-year contribution to a past year. The Lifetime ISA has a separate annual subscription limit of £4,000 (counting towards the overall £20,000). ISA contributions must be made between 6 April and 5 April of the relevant tax year. Transferring existing ISAs between providers does not count as a new subscription and does not affect your annual allowance. Flexible ISAs (offered by some providers) allow withdrawals and re-contributions within the same tax year without losing the allowance.
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.