Natalis was in office as archbishop from 746 to 747, but also the years 750 to 751 or 740 to 741 are proposed by scholars.
Almost nothing is known about the life and the episcopate of Natalis. The main source of information about his episcopate was a gravestone which was placed in the church of San Giorgio al Palazzo in Milan and which was still extant in the 16th century. From the copies of such gravestone it is known that Natalis governed the church of Milan for fourteen months, that he died at 72 and that he founded the church of San Giorgio, having obtained a donation, probably from Ratchis, king of the Lombards.
Other traditional information about his life, such as his surname Marinoni and his scholarship in Latin and Hebraic, have no historical basis.