11.1 The Actuary shall certify the sum or sums (inclusive of any ordinary contributions of Members) required from time to time to enable the Trustees to maintain the NATS Section and provide the Intended Benefits under the NATS Section. The Trustees shall arrange for written notice to be given to the Employers in the NATS Section specifying the proportions of such sum or sums certified to be applicable to their respective employees and the instalments (if any) by which the Trustees require the same to be paid.