Italy international Gianluca Scamacca has completed his move to Atalanta from West Ham United for a reported fee of €30m including bonuses.
The 24-year-old has put pen to paper after undergoing his medical tests over the weekend.
It is a permanent transfer for €25m plus another €5m in add-ons.
He had only left Serie A last summer in a deal worth €36m plus €6m in performance-related bonuses from Sassuolo, an agreement that also guarantees the Neroverdi a 10 per cent of the sell-on fee.
That means West Ham will only pocket at most €27m from the sale, as Sassuolo are owed €3m.
Scamacca spent time in the youth academies of Lazio, Roma, PSV Eindhoven and Sassuolo, before going on loan spells with Cremonese, PEC Zwolle, Ascoli and Genoa.
He found the net eight times in 27 competitive games for West Ham United, helping them win the Europa Conference League trophy.
The striker has 11 senior caps for Italy, but is yet to score his first goal.