By Liz Hoffman 

Morgan Stanley is making a play for the thousands of employees in the startup economy who might one day be millionaires.

The Wall Street bank will pay $900 million to acquire Solium Capital Inc., which manages the stock that corporate employees receive as part of their pay. The deal, the bank's largest acquisition since the financial crisis, is set to be announced Monday.

Solium's 3,000 corporate clients employ 1 million workers and include startups such as Stripe Inc. and Instacart Inc., whose employees tend to be younger and have fewer relationships with traditional financial firms. The luckiest will become millionaires overnight if their companies go public. Others could get wealthier over time and buy houses, plan for retirement and invest in the market.

Chief Executive James Gorman is betting he can convert them into clients of Morgan Stanley, whose wealth arm manages $2.3 trillion for 3.5 American households.

"Most people's money is coming through their workplace, so it's an obvious place for us to be," Mr. Gorman said in an interview.

Morgan Stanley's existing stock-plan business has about 330 corporate clients including Microsoft Corp. and Ford Motor Co. and covers 1.5 million employees. But it is geared toward top executives rather than rank-and-file employees, and Fortune 500 companies rather than startup darlings.

"We didn't historically have a way to serve them," Mr. Gorman said. "Now we do."

Morgan Stanley will pay 19.15 Canadian dollars a share for Calgary, Alberta-based Solium, a 43% premium over its Friday closing price of C$13.36, or about US$10. It expects the deal to close by June 30.

Regulators appointed by President Trump have signaled they are more open to acquisitions by big banks, particularly deals for steadier, less risky businesses.

Mr. Gorman has sounded more acquisitive as he has stabilized Morgan Stanley's business and increased its profits. The bank bought a small real-estate firm in 2018 and has been scouting takeover targets in asset management, the smallest of its four main businesses.

"Last year was the first time we felt comfortable that we could even consider [acquisitions]," he said in the interview. "We'd like to do more."

Morgan Stanley once considered getting out of the stock-plan business, where it was a distant competitor to Fidelity Investments Inc. and E*Trade Financial Corp. and lacked the digital offerings to serve less wealthy clients. In 2016, it outsourced its contracts to Solium.

Morgan Stanley recently launched an online wealth-management tool, where it can park smaller accounts until they are big enough to merit a human adviser. Employees in Solium's plans will start out there, said Andy Saperstein, who co-heads Morgan Stanley's wealth business. "We can incubate those relationships," he said.

Morgan Stanley also plans to build financial-wellness websites for employees.

Rival Goldman Sachs Group Inc. is doing the same, also in search of steadier revenues. The firm is expanding its Ayco business, which offers financial and tax advice to top-tier corporate executives, down through the employee ranks.

Solium earned C$81 million in revenue through the first nine months of 2018, up 29% from a year earlier. Its stock, up 30% over the past year, closed Friday within a penny of its all-time high. It has a contract with UBS Group AG's wealth-management arm, though it couldn't be determined whether that will continue after the acquisition.

Morgan Stanley said the acquisition wouldn't have a meaningful impact on its 2019 earnings or reduce its planned stock buybacks. The bank has regulatory approval to repurchase $2.6 billion in shares before June 30.

Write to Liz Hoffman at liz.hoffman@wsj.com

(END) Dow Jones Newswires

February 11, 2019 06:56 ET (11:56 GMT)