Metadata relating to what information is collected, and how it is transformed and processed to produce statistical output is critical for users' understanding the quality of the outputs produced. Best practice suggests that metadata should not be created retrospectively but rather created as a by product of various processes and stored internally. Critical information on concepts, sources and methods and quality issues should be made available along with the outputs produced. Directions to the availability of more detailed information for those users needing it should be included. While this approach applies to all statistical outputs regardless of their data source, there are usually some particular characteristics of outputs produced from administrative data which need to be drawn to the attention of users of the outputs. Any adjustments made to the data as a result of these features during the processing of the data should also be declared (e.g. editing, imputation etc.).
If possible it is important to obtain any information from the data custodians which can assist in interpreting the information accurately. It is also important to continually check that the reported structure of the file and its contents have not altered from one time period to the next.