What is the UK cash ISA allowance for 2025-26?

The overall ISA allowance is £20,000 for 2025-26. You can put up to that amount into cash if you wish, as long as you subscribe to only one cash ISA provider this tax year. Any unused room expires at midnight on 5 April and cannot be carried forward.

What changes in April 2027 for cash ISAs?

From 6 April 2027, adults under 65 are expected to face a £12,000 cap on cash ISA subscriptions. The overall ISA structure continues, but the lower cash limit means many savers should build their tax-free cash base sooner. Using today’s £20,000 limit helps offset that future cap.

Can I leave cash in a stocks and shares ISA?

You can hold small cash balances for trading and settlement, but HMRC has signalled penalties for leaving large amounts as cash for long periods. If money will sit uninvested, consider moving it to a cash ISA. Keep only what you need for fees and near-term trades in the investment account.

What if I cannot pick the best rate before the 5 April ISA deadline?

Open an easy access cash ISA now and fund it to secure this year’s allowance. After the deadline, use an ISA transfer to move to a better deal without losing tax protection. Confirm provider cut-offs, use Faster Payments, and keep screenshots or receipts for your records.

Global Market Insights

UK ISAs March 15: Last Chance to Max £20k Before 2027 Cash Cap

ByHuzaifa Zahoor March 15, 2026March 15, 2026

With 21 days until the 5 April ISA deadline, the UK cash ISA allowance of £20,000 is a use-it-or-lose-it shield for savers. From 6 April 2027, under-65 adults face an ISA allowance cut 2027 that caps cash at £12,000, and HMRC plans penalties for leaving cash inside stocks and shares ISAs. Now is the time to ring-fence interest from tax and adjust allocations. We set out fast, practical steps to fund, transfer, and choose products so your money is ready before rules change.