Lukaku's £75m transfer to Old Trafford is said to involve a £15m appearance-related clause that would mean another £15m to Everton.
The move wasn't confirmed until to day but Lukaku was already talking about his dream move on TV and on social media over the weekend.
Lukaku was interviewed by ESPN about his switch from Goodison Park to Old Trafford and, after expressing his delight at joining the "world's biggest club" with "the best fans", he sent a farewell message to the club he joined four years ago, initially on loan and then on a permanent basis from Chelsea for £28m:
I want to say a big thank you to all the people involved at @everton,". I want to thank the fans for your support throughout the 4 years we've spend together.
You guys helped me through all my games and I can proudly say it was an honour to play in front of you. To the staff at the the stadium and training ground thank you for making me feel home from the first day I walked in.To my teammates it was great to play with you guys. To the technical staff thank you for helping me become a better player. Working with you guys has been a pleasure and I'll take your advice throughout the rest of my career. Thank you Everton Football Club.