After 20 years at the helm, Klarna CEO Sebastian Siemiatkowski faces his biggest test yet: A U.S. IPO

Sebastian Siemiatkowski , 43 , has been CEO of Klarna for 20 years .

Klarna is synonymous with the "buy now, pay later" payment method.

The fintech firm is about to make its U.S. IPO debut in New York in the lead-up to the IPO .

Siemiatowski has faced a rollercoaster ride of ups and downs over his two-year CEO tenure.

He has faced criticism in the run up to an IPO that could value it at $15 billion .

Klarna co-founder and CEO faces biggest test yet — taking the business he co-founded two decades ago public.

Siemiatkowski is the second -largest shareholder with a 22% stake in Klarna .

The company hasn't yet set a date for when it will go public, nor how it will be priced.

A positive IPO outcome would also lift the value of Klarna employees' stakes, and potentially boost morale after a turbulent few years for the company. "It's a balance between finding a fair value for existing investors looking to cash out and new investors seeking a stake in Klarna at a fair price. Overvaluing the company could lead to its valuation falling in the future. While undervaluing it may mean money has been left on the table for those exiting," Patel said..