The National Minimum Dataset (NMDS) File Specification describes the file format that is used to send information to National Collections for inclusion in the NMDS. This includes the file layout and, to a lesser extent, the business rules used for validating the data items within the file.

There are two audiences for this document:

  • Software developers designing, implementing and altering provider systems to ensure that they export information in a format suitable for loading into the national collection.
  • Business analysts verifying that all required data elements are present and specified correctly.

If a previous version of the NMDS File Specification is required contact us on

The NMDS File Specification document should be read in conjunction with the National Minimum Dataset (Hospital Events) Data Dictionary.