La cambiale di matrimonio (The Bill of Marriage or The Marriage Contract) is a one-act operatic farsa comica by Gioachino Rossini to a libretto by Gaetano Rossi. The libretto was based on the play by Camillo Federici (1791) and a previous libretto by Giuseppe Checcherini for Carlo Coccia's 1807 opera, Il matrimonio per lettera di cambio. The opera debuted on 3 November 1810 at the Teatro San Moisè in Venice  Composed in a few days when he was 18 years old, La cambiale di matrimonio was Rossini's first professional opera. The overture, written when he was a student at the Liceo Musicale in Bologna, is an important part of the modern concert repertoire. As was to become typical of his later career, the duet "Dunque io son" was later reused, to greater effect, in act 1 of The Barber of Seville