(REUTERS) - Diego Costa's return to LaLiga side Atletico Madrid from Jan 1, 2018 has been finalised, Premier League champions Chelsea said in a statement on Tuesday.
The two clubs agreed the transfer last week and on Monday, the 28-year-old Spain forward passed a medical to return to the Spanish capital.
"Diego Costa has today agreed terms for his transfer to Atletico Madrid, which will take effect on Jan 1, 2018," Chelsea said in a statement.
"We thank Diego for his efforts and wish him well in his future career."
The controversial Brazilian-born striker's departure from Stamford Bridge signalled the end of a messy transfer saga during which Costa claimed Chelsea manager Antonio Conte had told him via text message that he was no longer required at the club.
His last game for Chelsea came at Wembley in May when he scored in the 2-1 FA Cup final defeat against Arsenal.
Costa leaves Chelsea having won two Premier League titles and one League Cup, and he scored 59 goals in 120 appearances - finishing as Chelsea's top scorer in each of his three seasons at the club.
"I'm very happy to return home," Costa said in a statement on Atletico's official website.
"I've always said it, Atletico is my home. I'm very, very happy. I'm looking forward to start contributing. I'm going to give my all for the team, as I always try to do.
"Thank you to the whole club for making this move forward, I'm very grateful to everyone."
Costa will have to wait before pulling on the red and white striped shirt of Atletico as the European transfer window is closed and Atletico are banned from registering new players until 2018 after breaching Fifa rules.
Costa, who will wear the No. 18 shirt, will join the team's training from Wednesday and will be eligible for selection from Jan 2 when the Spanish transfer window opens and Atletico's ban ends.
Costa first joined Atletico in 2006 and following a string of loan spells, established himself as a key part of Diego Simeone's title winning side in 2013-14 before joining Chelsea in a deal worth £32 million (S$58 million).
Atletico are in the same Champions League group as Chelsea, but their two clashes will both be before Costa is eligible to continue his career with the Spanish club.