§1. Every Five years a diocesan bishop is bound to make a report to the Supreme Pontiff on the state of the diocese entrusted to him, according to the form and time determined by the Apostolic See.
§2. If the year determined for submitting a report falls entirely or in part within the first two years of his governance of a diocese, a bishop can refrain from making and submitting his report on this one occasion.
Source: Code of Canon Law (Vatican.va)