Adult cash ISA balances surged in 2025 as savers moved their finances ahead of the November Budget, Paragon Bank has highlighted.

Analysis by the bank showed that cash ISA balances increased by over £50bn, as non ISA balances fell.

Paragon analysed CACI data for the period between January and October 2025 which indicated that savers moved decisively towards tax-efficient savings ahead of the anticipated reduction in the cash ISA allowance announced in the Budget.

Over the period, the average adult cash ISA balance increased from £15,919 to £17,019, while the average non-ISA balance fell from £11,918 to £11,710. Paragon said the data suggests that savers were seeking to maximise tax-free interest before potential changes would reduce the cash threshold.

At the Budget, the Chancellor, Rachel Reeves, announced a reduction in the cash ISA allowance from £20,000 to £12,000, which will come into force from April 2027.

Across the period analysed by Paragon, total adult cash ISA balances climbed by £51.4bn, with much of the growth driven by demand for fixed term products. Overall, adult cash ISA balances in accounts totalled £430.1bn across 25 million accounts at the end of October.

Fixed term ISAs accounted for £30.9bn of the overall uplift, as balances rose to £232.8bn with customers locking in rates ahead of an expected reduction in interest rates and movement in the tax-free savings landscape. Instant access ISA balances also grew, albeit at a steadier pace, increasing by £21.4bn to close October at £191.9bn.

By contrast, non-ISA balances fell by £8.7bn over the same period to £838.8bn across 71.6 million accounts.

Paragon’s head of savings, Andrew Wright, said that the data “clearly shows that savers were preparing for change”.

“With widespread expectations that the Chancellor was planning to reduce the cash ISA threshold in the Autumn Budget, many savers were clearly looking to protect more of their savings from tax,” Wright said.

“We’ve seen particularly strong uptake of fixed-term ISAs, as savers secured attractive rates ahead of the base rate reduction in December while maximising their tax-free returns. The shift away from non-ISA balances reflects a growing awareness that relying on the personal savings allowance alone is no longer enough for many people, especially as rates remain elevated.”

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