[EN] The manuscript 9/1784 of the Library of the Real Academia de la Historia (Royal Academy of History), known as Registro de Cortes or Libro de Cortes (Registry of Parliament/Book of Parliament), contains a collection of simple copies made by the court scribes and lawyers of the Castilian Cortes (Parliament) at the beginning of the 16th century, in which numerous documents for internal use from the time of John II of Castile, Henry IV of Castile and the Catholic Monarchs were collected. Its time span covers the period between 1425 and 1502. The Registry’s texts allow us to understand the operation of the parliamentary institution in numerous matters that are not included in the ordenamientos (ordinances) and the cuadernos de peticiones (n...