A method, for use for example in pension scheme defeasance, comprises providing to an entity a financial instrument which undertakes to pay to the entity, at regular points in time within a specified duration, sums according to a schedule of payment amounts associated with the financial instrument, the scheduled payment amounts being arranged to match with the expected cash flow obligations of a pension scheme to its members. At a re-set point in time the schedule of payment amounts is re-set such that the entity will receive an adjusted payment amount calculated to be the aggregate of nominal cash flows to be paid to the pension scheme members adjusted to take into account the actual cumulative mortality experience of the pension scheme prior to the re-set point in time. Calculations for carrying out the method may be made using a data processing system.