From www.mutopiaproject.org

The Piano Sonata No. 14 in C minor, K. 457, by Wolfgang Amadeus Mozart was composed and completed in 1784, with the official date of completion recorded as 14 October 1784 in Mozart's own catalogue of works. It was published in December 1785 together with the Fantasy in C minor, K. 475, as Opus 11 by the publishing firm Artaria, Mozart's main Viennese publisher.
The above text from the Wikipedia article "Piano Sonata No. 14 (Mozart)" text is available under CC BY-SA 3.0.