Osborne was recently appointed editor of the Evening Standard, and also hold roles at BlackRock, his Northern Powerhouse consultancy and as a public speaker.
It comes just weeks after Osborne defended his decision to edit the newspaper while remaining as an MP for the constituency of Tatton.
The newspaper revealed Osborne's decision, with the Conservative writing to constituents to say that he would continue fighting for issues closest to him.
However, the former chancellor did not rule out a political comeback, stating only that he was leaving Westminster "for now".
“At the age of 45, I don’t want to spend the rest of my life just being an ex-chancellor. I want new challenges.
“I’m very excited about the opportunity to edit the Evening Standard. I’ve met the team there, and their energy and commitment to this great newspaper are positively infectious.”
First entering into parliament in 2001, he had maintained since losing the top role that he wanted to contribute to parliament.
In a debate on 20 March, Osborne told MPs: "In my view, this Parliament is enhanced when we have people of different experience taking part in our robust debates and when people who have held senior ministerial office continue to contribute to the decisions we have to make."
But the former chancellor has faced repeated criticism for his willingness to take up roles outside parliament.
Osborne follows his former ally Cameron in departing Westminster. Cameron had also stated that we would remain as a backbencher, but ended up quitting the role just months into the new parliament.