Trustees review the funding of Defined Benefit pension schemes every three years, with the help of the Scheme Actuary. The size of any deficit and the agreed recovery plan dictate the amount that you, the employer, will need to pay into the scheme over the following three years.
Trustees are required to be cautious in scheme funding, and to make prudent assumptions. But if they’re too prudent, they will ask you to pay more than necessary into the scheme.