The Tokyo Regional Taxation Bureau has found that a unit of the developer of online game Fortnite failed to report some ¥30 billion in revenue from in-game spending, sources said Wednesday.

The problem, which lasted for three years to December 2020, was uncovered in an investigation by the tax bureau.

The bureau concluded that some ¥3 billion in consumption tax was left undeclared, slapping the unit with back taxes and penalties reaching an estimated ¥3.5 billion. It is believed to be an unusually large amount imposed on a foreign company as a result of a tax investigation.

Fortnite is a popular online game developed by Epic Games of the United States. It is estimated to be played by over 400 million people worldwide via personal computers, game consoles or smartphones.

The game is free to play, but players can make in-game purchases of some virtual items.

Subject to the tax investigation was a Luxembourg unit of Epic Games, the sources said, adding that the unit did not report revenue from in-game spending by players in Japan.