This paper addresses Information Systems (IS) standards from a managerial perspective. Standards

can be seen as behavior regulations where there is a lack of hierarchical and market steering

mechanisms. The use of government standards to harmonize IS is complicated, since in comparison to

hardware and software products, IS are specific to the context in which they are implemented. Only

hardware and software can be pre-fabricated. Based on a comparative case study of implementations

of regulation from the European Commission seeking to harmonize European e-Customs, this paper

develops a taxonomy of deviation sources for IS standards implementation divergence – reasons why

implementations of IS standards differ. In addition to the previously known deviation sources: a) work

process, b) data meaning, and c) data model, we found two new potential deviation sources in mode of

transfer, and timing of implementation. Furthermore, all these sources seems to be of the nature that

even the slightest deviation in any of the areas leads to the standard failing to meet its objective of

increased efficiency with detrimental effects to the competitiveness of European exporters.