In the past couple of months, in the run up to Uber's IPO this week, Uber employees on occasion have asked CFO Nelson Chai during internal meetings whether they should sell their shares once they’re able to, when lock-up restrictions lapse six months after the company goes public. Rather than exhort employees to hold onto their stock, Mr. Chai’s standard response has been more neutral. “Go talk to a financial adviser. That’s a personal decision,” he has said, according to people who have some of these exchanges. 

In the seven months since joining Uber, the 53-year-old Mr. Chai has won a reputation among the company’s rank and file for candid responses to tough questions. Even more importantly, he has proved willing to tackle Uber’s heavy losses head-on, by cutting some costs and imposing discipline on hiring managers, say people who work with him. In order to unlock bigger budgets, executives now must present arguments for how new investments will pay themselves back. Expense reports are being rejected with higher frequency, these people said. Mr. Chai has also taken steps to seal gaps in Uber’s financial controls.