The changes will allow multiple subscriptions to ISAs of the same type every year from April.

They will also open the door to partial transfers of ISA funds between providers and enabling some fractional shares to become eligible ISA investments.

While a number of changes have been made, the annual £20,000 ISA saving allowance has been frozen for a further year from April.

The key changes include:

• Multiple subscriptions can be made to ISAs of the same type every year from April (within the annual savings limit)
• Savers will no longer need to reapply for an existing ISA
• Partial transfers of ISA funds can be made in-year between providers
• Certain fractional shares contracts will be eligible ISA investments
• Long-Term Asset Funds (LTAFs) and open-ended property funds with extended notice periods will become permitted investments in Innovative Finance ISAs
• The account opening age for ISAs will be harmonised for any adult ISAs to 18 from April

In the Autumn Statement documents the Treasury says: "The government is making changes to simplify ISAs and provide more choice, meaning it will be easier for people to choose the best ISA accounts for their needs and move money between them. This involves digitalising the ISA reporting system to make it more effective, as well as expanding the investment opportunities available in ISAs to include Long-Term Asset Funds and open-ended property funds with extended notice periods."

Lisa Laybourn, director of technical policy and risk at TISA, said: “Our recommendations over recent years focussed on addressing the limitations and complexities within the system, fostering an environment where investing is more accessible and rewarding for all.

“This package of measures from the government has considered many of these asks, making it more accessible, flexible, and advantageous for all savers, especially those planning for retirement and self-employed people.”

Sarah Coles, head of personal finance, Hargreaves Lansdown, also welcomed the changes.

She said: “Savers and investors will be delighted the Chancellor has taken the opportunity to pay some much-needed attention to ISAs to help ensure this much-loved part of the furniture remains a firm fixture for the future.

“Allowing multiple ISAs of the same kind in a single tax year from April, and partial transfers of ISAs opened in the current year are both sensible ways to inject much-needed flexibility and simplicity into the system. For cash ISA savers, it offers the opportunity to jump on more competitive deals, if they become available later in the tax year.

“For those using stocks and shares ISAs, it protects investors who accidentally open more than one ISA of the same type in a tax year. If you make a single regular payment into a stocks and shares ISA at the start of the tax year, and then try to invest in another stocks and shares ISA on the last day of the tax year, you’ll break the rules. The second ISA provider may end up refunding your money and you could miss a big chunk of your allowance for that year. This change would remove that risk.

“There are also a number of smaller technical changes which will ease some of the frustrations of the system, including the fact that from April people will no longer need to reapply for an existing ISA.”