Uber's Chief Financial Officer is stepping down.

Uber CFO Brent Callinicos announced his resignation through a memo where he said quitting the job is a fulfillment of his promise to spend more time with his family.

"For me, there is no later. It is now. It is time to do what I have desired for a very long time; time to keep a promise to my wife of not missing another school play, swim meet, or academic achievement of our daughter's childhood," Callinicos wrote.

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Uber CEO Travis Kalanick said Callinicos will stay on as an adviser to the company.  He also told investors that a replacement has yet to be named.  Kalanick praised Callinicos for his significant role in helping the company grow fast.

"Brent has done a wonderful job here at Uber but has decided that it is time for his next journey, one where his wife and daughter take the front seat,"  Kalanick said.

Callinicos had only been with Uber for two years since he joined in Sept. 2013.  It was during his time that the online taxi service saw its fastest years of growth.  He previously served as Vice President, Treasurer and Chief Accountant at Google.  He also held positions at Procter & Gamble, Disney and Microsoft.

His move to leave the company comes at a time when Uber is speculated to go public this year.  This could mean not an ideal time for a company to deal with key personnel movements, particularly within its financial department.

Callinicos' second man on Strategic Finance will temporarily take his place, until a new CFO is named. 

The fast-growing car sharing service was recently valued at $41 billion after its latest funding round.  That was more than double its June 2014 value at $18.2 billion.  Its investors include Goldman Sachs and Google Ventures.

Callinicos is the second financial chief of a major company in Silicon Valley that has quit their jobs in just a week, citing family as a reason. 

Last week, Google CFO Patrick Pichette said he was stepping down to travel the world with his wife, in what he calls a "perfectly fine mid life crisis."

TagsUber, online taxi, taxi, CFO, brent callinicos