The BT Pension Scheme (BTPS) will close to future accrual for managers in May 2018, and will them into the telecoms giant's defined contribution (DC) scheme.
The announcement is the result of months of negotiations with the union Prospect following a consultation on the future of the company's DB scheme, which finished on 17 January.
Prospect secured improvements on BT's original plans, including members in the old scheme being moved into the DC offering - the BT Retirement Saving Scheme (BTRSS) - from 1 June this year rather than 1 April.
Also, managers in BTPS will be able to continue making additional voluntary contributions into the old scheme after it closes - until 31 September 2019 - therefore covering two further financial years and two bonus cycles.
In addition to agreed transition payments, the period for additional employer contributions to those transferring has been extended from three to five years up to 31 May 2023. During that time BT will pay 11% of salary for managers paying 8% of salary into the DC scheme.
From 31 May, BT will introduce an option for managers aged 55 or over to draw their BTPS pension while continuing to work for BT for a further two years.
Managers aged 55 plus who want to retire early will have the DB part of their pension actuarially reduced by a smaller amount - likely to be 3%-3.5%, from 1 June this year.
BT has also agreed with Prospect that managers currently in the BTRSS will receive an increase in employer contributions to a maximum of 10% from 1 June. The DC offering has been open to all employees joining the company since 2001.
Prospect national secretary Philippa Childs said: "During a very difficult negotiation we secured decent protections for those having to transfer for future service, as well as improved employer contributions for people already in the BTRSS.
"Since the ballot result, and the end of BT's own consultation with staff, we have gone back to the employer and won yet more concessions."
BT Group HR Director Alison Wilcox said: "We are working hard to ensure fair, flexible and affordable provision for members of our pension schemes."
In regards to the situation for team members - employees other than managers - BT is still reviewing feedback and will continue to discuss this with the Communication Workers Union before making a final decision.
The deal came days after BT announced it would appeal last month's High Court ruling, which barred it from switching indexation for one section in BTPS from the Retail Prices Index to the Consumer Prices Index.
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