LONDON — TikTok’s turnover in Europe grew 545% to $170.8 million last year as advertisers upped their spending on the platform, according to a filing with the U.K.’s company registry on Monday.

The filing, submitted to Companies House, shows how TikTok has invested heavily in scaling up its European business as it looks to take on rivals like Facebook, Instagram, YouTube, and Snap.

Losses at the Chinese-owned firm soared from $118.7 million in 2019 to $644.3 million in 2020.

A TikTok spokesperson told CNBC that the results “reflect an exciting period of growth for the business.”

“We saw revenue increase significantly as our community grew, and we’ve continued to invest aggressively in building a solid foundation for the long-term success of the platform,” they said.

Staff has been one of TikTok’s biggest expenses. The company’s headcount in Europe rose by over 1,000 people last year, going from 208 in 2019 to 1,294 in 2020. TikTok declined to comment when CNBC asked how many staff it has elsewhere in the world. But in July the firm said it wanted to increase its U.S. workforce from 1,400 to 10,000.

Beyond staff, TikTok also spent $344.9 million on selling and marketing expenses in 2020, up from $110.3 million in 2019, according to the filing.

TikTok’s popularity has boomed in the last three years and last week it announced that it has 1 billion monthly active users on its platform, up 45% on July 2020.

TikTok said it had about 55 million global users by Jan. 2018. That number grew to more than 271 million by Dec. 2018 and 507 million by Dec. 2019. The company reported nearly 700 million monthly active users last summer.

But TikTok is aware that the growth may not last forever. The company, which is owned by China’s ByteDance, noted under a “business risk” section that it “faces competition from internet companies that operate content-based social platforms.” Indeed, Facebook and Snap are among TikTok’s biggest competitors and they’re all fighting for advertising dollars.

The size of these social media companies has led them to come under increasing levels of scrutiny from regulators in recent years. Under a “compliance risk” section of the filing, TikTok noted that it is “subject to a range of new and existing laws in a regulatory landscape that can change.”

The company has faced a number of setbacks, including a possible U.S. ban after the former Trump administration deemed its data storage and security a national security risk.

TikTok was to be sold to an American company if it wanted to keep operating widely, with Oracle later being named as its “trusted technology provider.”

However, President Joe Biden’s ascension to the White House allowed the company to continue operating as normal. In February, The Wall Street Journal reported that the Oracle deal had been “shelved indefinitely.” Biden this summer also signed an executive order that sets criteria for the government to evaluate the risk of apps connected to foreign adversaries.

The dramatic increase in TikTok’s European headcount comes even though some people have been turning down jobs at the video-sharing company over fears that it has a so-called 996 culture.

The 996 culture is practiced by some companies in China. The name is derived from the employees’ requirement of working from 9 a.m. to 9 p.m. for six days in a week, which works out at 72 hours per week. Meanwhile, the norm in the U.S. and the U.K. is around 40 hours per week, although many workers go over this. It’s illegal to work more than 48 hours per week in the U.K. on average. TikTok denied that such a culture exists.

“Like any fast-growing start up, employees work hard at TikTok and some functions occasionally have emergency off-hours work, but we absolutely do not have ‘996′ policies,” a spokesperson told CNBC in May.

They added: “Teams like user support or safety, whose work requires round the clock coverage, stagger on-call hours to arrange continuous service for our customers. As our employees continue to scale, requests that fall outside of working hours are the exception rather than the norm.”

— Additional reporting by CNBC’s Jessica Bursztynsky.