Klarna cut its outlook for a key metric as it expects softness in consumer spending to continue, particularly in Germany, its largest market by volume.

The payments company also said it is searching for a new finance chief, with Niclas Neglén planning to step down from the role early next year.

Shares tumbled 21% to $15.41 Tuesday, extending their roughly 46% decline year to date.

Klarna now expects gross merchandise volume, which measures the total monetary value of all completed purchases over its network, of $149 billion to $151 billion for the year, down from a prior forecast of at least $155 billion. Analysts polled by FactSet expected gross merchandise volume of $155.68 billion.

Neglén said on a call with analysts that the lower outlook includes a roughly $600 million impact stemming from currency translations, as well as softer-than-expected discretionary spending among German consumers.

"This is consistent with what you have heard across German retail this season," he said. "Our guidance simply assumes Germany stays softer, rather than recovering."

U.S. volume assumptions remain unchanged, and the U.S. continues to be Klarna's fastest-growing region, Neglén said. Overall, the company is winning over more customers and merchants. Klarna ended the latest quarter with about 120 million active customers, up about 8% from a year earlier, while its merchant network grew 54%, to about 1.21 million.

Klarna's buy now, pay later loans continue to drive growth, while the expansion of higher-engagement products, such as longer-term installment loans and the Klarna Card, are providing a boost to transaction margin dollars, Chief Executive Sebastian Siemiatkowski said.

Transaction margin dollars, or total revenue less total transaction costs, grew 42% during the latest quarter. The company set its full-year outlook for transaction margin dollars to between $1.62 billion and $1.65 billion, compared with a prior outlook of at least $1.61 billion.

For its three months ended June 30, Klarna swung to a profit of $9 million from a loss of $53 million a year earlier. On a per-share basis, quarterly earnings of one cent came in ahead of analyst expectations for a quarterly loss of five cents.

Total revenue jumped 27% to $1.04 billion and came in ahead of Wall Street models for $996.5 million. Gross merchandise volume rose 18%, to $36.65 billion.

Looking ahead, Klarna guided for revenue of $940 million to $980 million in the current quarter, below Wall Street models for $1.11 billion.

Klarna also on Tuesday said its chief marketing officer, David Sandström, plans to step down early next year.