United haggled over a deal for Lukaku throughout last summer but sold the Belgian striker last August after he failed to appear during their pre-season tour of Australia and Asia before going AWOL.
At the time, it emerged United had accepted a bid worth up to £73.9m but Inter’s accounts have disclosed the figure was €74.162 – around £66.75m.
United were holding out for £80m for Lukaku as they were reluctant to take a hit on the £75m they paid Everton for him in 2017. However, Lukaku’s disruptive behaviour towards the end of his time at the club effectively forced United’s hand and Inter capitalised with their second bid.
Ashley Young left United for Inter in January and cost precisely €1.729m (£1.55m). United communicated at the time they had received €1.5m, plus some add-ons.
Inter are also confident of securing a permanent deal for loanee Alexis Sanchez, who has entered the last two years of his United contract.
United negotiated a sell-on clause as part of the Lukaku deal as the 27-year-old has commanded £196.7m in transfer fees throughout his career.
Lukaku effectively torched his relationship with United manager Ole Gunnar Solskjaer by posting running statistics from a training session on Twitter. Solskjaer rebuked Lukaku and told him to train with the Under-23s.
Instead, Lukaku headed to former club Anderlecht on the first-team players’ day off and stayed there the next day while his teammates reported at United’s Carrington training complex.