Cash ISA balances surged in 2025 as savers flocked to protect tax-free returns ahead of the Autumn Budget.
Analysis from Paragon Bank showed that over the course of 2025, the average adult cash ISA account balance increased from £15,919 to £17,225, while the average non-ISA account balance fell marginally from £11,919 to £11,909.
Total adult cash ISA balances rose by £57 billion during the period, with much of the growth driven by strong demand for fixed-term products. Overall, adult cash ISA balances in accounts totalled £436 billion across 25 million accounts at December 2025.
Fixed-term ISAs accounted for £35.8 billion of the overall uplift, rising to £237.7 billion, while instant access ISA balances grew by £22.4 billion to £192.9 billion.
In contrast, non-ISA balances fell by £1.8 billion over the same period to £845.6 billion across 71 million accounts. This was mainly driven by fixed-term non-ISA balances falling as savers reallocated money into tax-efficient wrappers.
Andrew Wright, head of savings at Paragon, said: “2025 marked a clear shift in saver behaviour, with many people taking proactive steps to protect their returns by making greater use of tax-efficient savings. Anticipation of changes announced in the Autumn Budget encouraged savers to review where their money was held and to maximise the benefits of cash ISAs while allowances remained unchanged.
“What’s particularly notable is the strength of demand for fixed-term ISA products. Savers were not only responding to potential tax changes but also looking to lock in competitive rates amid expectations that interest rates would begin to fall. This combination of tax planning and rate certainty made fixed-term ISAs especially attractive.”
