We were asked to perform an audit of a series of spreadsheet financial models which our client, a major company in the nuclear industry, had designed and built to forecast its accounts for the next fifty years. Several of the models, which had all been built by different members of the clients staff, forecast information such as reactor fuel burn costs, fuel reprocessing costs and decommissioning costs. This information was transferred to a central model that forecast the company's financial statements. Our review was designed with four objectives in mind: We were able to make recommendations for improvement in relation to all four of these objectives, and also provided advice to our client on a number of principles of good financial modelling.

• the models should be arithmetically accurate, that is all the formulae should be consistent;
• the logic of the models should be correct, that is they should operate in the way their designers intended them to;
• the procedures surrounding the use of the models should be well defined: changes to the logic of the models should be fully documented and reviewed, and different scenarios of the models should use consistent data;
• the models should be consistent with the client's accounting policies.