The Efficiency Decoration, post-nominal letters TD for recipients serving in the Territorial Army of the United Kingdom or ED for those serving in the Auxiliary Military Forces, was instituted in 1930 for award to part-time officers after twenty years of service as an efficient and thoroughly capable officer. The decoration superseded the Volunteer Officers' Decoration, the Colonial Auxiliary Forces Officers' Decoration and the Territorial Decoration.

The Efficiency Decoration (South Africa), post-nominal letters ED, was instituted in 1930 for award to efficient and thoroughly capable part-time officers in the Citizen Force of the Union of South Africa after twenty years of service. The decoration superseded the Colonial Auxiliary Forces Officers' Decoration.