Benchmarking and comparisons of costs and performance measures have become important tools to improve community services and to make sure that monopoly enterprises are efficiently run. If the comparisons are to be useful, it is important that cost data and measures are comparable and consistent. Accounting data are often used in this kind of comparison. A harmonized model of accounting applied across compared enterprises is therefore important. However, harmonization is not enough. This paper aims to show that any principles applied must also lead to robustness in the accounting model used, so that the resulting accounting data are reliable and comparable regardless of any differences in the conditions of the various organizations.