Kimi Raikkonen admits he decided to leave Lotus because the Formula One team had not been paying him.
Last week it was confirmed that the 2007 World Champion would return to Ferrari next season after two years with Lotus.
The announcement came after weeks of speculation in which Lotus maintained several times that they would do all they could to retain the Finn.
However, in the end, the team's failure to pay his salary on time was the deciding factor for the 33-year-old.
"The reasons why I left are purely on the money side and I haven't got my salary," he said. "It's unfortunate."
He added: "I never had a bad feeling with them I knew my contract would end at the end of this year so I needed to make a decision.
"There were a lot of things (Lotus could have done to keep him) and they know what it is. It's hard to say what would have happened if they had done them."
As for his decision to return to Ferrari, Raikkonen does not believe he'll have any issues despite leaving the team at the end of 2009 after the two parties decided to end their partnership early in the wake of criticism leveled at the Finn.
"I know the team and the people, mostly the same. I don't think this will be too different to go there. The car is different so that will be the hardest part."
Raikkonen also downplayed a host of negative opinions about his soon-to-be partnership with Fernando Alonso with many predicting an acrimonious situation.
"I don't see why it wouldn't work we are old enough to know what we are doing," he said.
"If there is something I'm sure we can talk it through. It's not like we are 20 year olds. For sure there will be hard fights on the circuit."