The rules of an occupational pension scheme ( www.practicallaw.com/8-107-6900) that is in an assessment period or admitted to the Pension Protection Fund ( www.practicallaw.com/7-205-4059) (PPF) in accordance with which the trustees or the PPF, as appropriate, calculate and pay benefits to the scheme members. The admissible rules are the scheme rules in force at the start of the assessment period ( www.practicallaw.com/5-205-4060) but excluding:
Changes to the scheme rules within three years of the start of the assessment period if the change increases the scheme's liabilities.
Rules that only come into effect if the employer experiences an insolvency event.
(Paragraph 35, Schedule 7, Pensions Act 2004)