Kulusevski joined the Premier League side from the Serie A club on an 18 month loan in January last year with an option to buy for 35 million euros ($38.27 million).
British media reported a reduced 25 million pound ($32.04 million) fee had been agreed.
Kulusevski scored with an assist on his first league start for Spurs, a 3-2 victory over Manchester City in February 2022 and made 37 appearances last season.
Tottenham last week appointed Australian former Celtic coach Ange Postecoglou as their new manager.