The independent data regulator in the U.K. has fined TikTok 12.7 million British pounds, or about $15.9 million, for allegedly misusing the data of children under age 13, it announced Tuesday.

The Information Commissioner's Office says TikTok did not take enough action to ensure users younger than 13 weren't on the app, and that it used their data without parental consent.

TikTok UK's terms of service say a user must be at least 13 to join the app.

"We monitor for underage use and we will terminate your account if we reasonably suspect that you are underage," the terms say.

The ICO says up to 1.4 million children under age 13 used the app in 2020, and that between 2018 and 2020, TikTok did not provide "proper information to people using the platform about how their data is collected, used, and shared in a way that is easy to understand.

"Without that information," the ICO continued, "users of the platform, in particular children, were unlikely to be able to make informed choices about whether and how to engage with it."

In the U.S., the app has been under scrutiny over the last few years amid concerns about the Chinese government using it for spying and its effect on young people's mental health.

It has been banned on devices issued by the U.S. federal government and a blanket ban has been discussed in Washington.

Canada, the U.K., New Zealand and Australia have also banned the app from federally issued devices.

Last month, TikTok CEO Shou Chew testified before Congress last month and said thatTikTok does not promote or remove content at the request of Chinese authorities.

The app is "free from any manipulation from any government," he said.

"TikTok should have known better," UK Information Commissioner John Edwards said. "TikTok should have done better. Our £12.7m fine reflects the serious impact their failures may have had."