Sarah Coles, of Hargreaves Lansdown, said: “Providing certainty over allocations until 2030 brings very welcome stability to this cornerstone of public finances.

“The downside of this certainty is that over time the allocation will continue to fall in real terms and become less valuable.”

Only a minority of savers invest the maximum amount in Isas each year. The average amount deposited by an adult last year was £5,797.

There were fears Ms Reeves would reduce the amount that can be accumulated in an Isa over her lifetime. She previously called for a limit of £500,000 and wrote in a newspaper column for The Independent in 2016 said the Isa system needed an ‘overhaul’.

However, no major reforms were announced in the budget and no lifetime caps will be introduced. The only change was the expected abandonment of Jeremy Hunt’s Great British Isa project.

Isas were introduced in 1999 to replace Personal Equity Plans (Peps), introduced by the then Chancellor Nigel Lawson. The Isas investment allowance was originally £7,000, and for cash Isas it was £3,000. These limits remained in effect for nine years before multiple changes were introduced between 2008 and 2017.

Duty free packaging is a popular savings product, with more than half of the adult population using it. Official figures show the value of all adult Isas in the UK is £726 billion.

Ms Reeves’ decision to freeze annual deposit limits until 2030 marks a record period during which Isa allowances remain unchanged.

Budget documents show the Treasury will gain £15m in 2026-27, £90m in 2027-28, £265m in 2028-29 and £605m in 2029-30 from the freeze allowances.

A Treasury spokesperson said: “The average subscription is around £6,000 for all ISA types, making the £20,000 limit appropriate for the vast majority of savers. »