The document archiving system at the Toba Regency KPU is still done manually and takes a very long time. The purpose of "Document Archiving Design at the Toba KPU Using the Mixture Modeling Method" is to facilitate the Toba KPU agency in archiving incoming and outgoing letters. The Mixture Modeling method used serves to classify the types of letters based on the categories of letters that exist in the Toba KPU. The implementation of making this filing system uses PHP and MySQl programming.