The taxman has already issued one set of regulations, the changes from which will become effective from 6 April.

However, it said in a newsletter today that it has identified other areas that need changing and will issue another set of regulations to make changes retrospectively after 6 April.

HMRC said the changes would be minor and technical but it did not go into further detail.

Platform and SIPP provider AJ Bell said it hopes the changes will include giving pension savers with enhanced protection a higher lump sum allowance (LSA), as well as clarification for those who have scheme-specific lump sum protection.

Tom Selby, director of public policy at AJ Bell, said: “The decision to abolish the lifetime allowance was a huge positive for savers, removing an unfair tax penalty for long-term saving and removing one of the key barriers to senior public sector staff, including NHS consultants, taking on extra hours for fear of facing a tax charge as a result. However, the changes have been rushed and there are still issues that will not be resolved by the time the new rules are in place on 6 April.

“As a result, the Government will need to make changes to the rules post-implementation. This is far from ideal and means financial advisers, savers and providers will find the switch to the new regime this year hugely challenging. This clearly increases the risk of things going wrong and runs counter to the FCA's Consumer Duty, which requires firms to avoid foreseeable harm.”

For the 2022/23 tax year the lifetime allowance was £1,073,100, with the maximum amount of pensions tax-free cash someone can build up in their lifetime usually limited to 25% of this, or £268,275. Any excess above this lifetime allowance was subject by HMRC to a lifetime allowance charge of either 25% (if taken as income) or 55% (if taken as a lump sum).

In the 2023 Spring Budget, Chancellor Jeremy Hunt said the government intended to abolish the lifetime allowance altogether. Changes brought into force in April 2023 retained the lifetime allowance in the tax system but removed the lifetime allowance charge.

The Finance Act 2024 set out the main legislation for the abolition of the lifetime allowance, including an unusual clause allowing the Treasury to make subsequent changes to the primary legislation through regulation.

The lifetime allowance will be fully removed from the pension tax rules from April this year, leaving a tax regime where consumers can take as much income as they want from their pension and checks will only be made on lump sums taken.

Under the new regime, a Lump Sum Allowance set at £268,275 is the maximum someone can take as a tax-free lump sum (unless they have protection). This is a quarter of the current £1,073,100 LTA.

A Lump Sum and Death Benefit Allowance, set at £1,073,100, incorporates both tax-free lump sums someone takes while alive and lump sums paid on death.

There will be a third allowance – an overseas transfer allowance – also set at £1,073,100, measuring the value of pension benefits transferred to qualifying overseas pension schemes.