Allen's 34th touchdown pass of the season surpassed Kelly's previous franchise record of 33 set in the 1991 season.
Kelly, a Hall of Famer and perhaps the most revered Bills player of all-time, led Buffalo to a Super Bowl appearance that season, while Allen has keyed Buffalo's rise to its first AFC East title since 1995.
Allen tied the record with an 18-yard scoring strike to Stefon Diggs earlier in the third quarter.
It was an all-around stellar night for Allen in terms of single-season accomplishments, as he joined another Hall of Famer Steve Young as the only players in NFL history to surpass 4,000 yards passing, 30 passing touchdowns and five rushing touchdowns in a season, per NFL Research.
Allen's night ended with much of the fourth quarter still to be played. He was stellar. Allen completed 27-of-36 passes for 320 yards, four touchdowns and no interceptions.
Through 15 games, Allen's 377 completions and 34 touchdowns are each franchise records and with his eighth 300-yard game of the season on Monday, he established another Bills record.
It's been quite a season for Allen and he's still got one game left.