Apple and Google are already facing scrutiny in the wake of a South Korean law requiring that they allow third-party payments. Reutersreports the Korea Communications Commission (KCC) will investigate Apple, Google and SK Group’s One Store over potential violations of the in-app payment law. Regulators said they started inspecting the digital shops on May 17th, and found enough to be concerned all three might have broken the rules.

It’s not certain just how the firms might have violated the law. MacRumorsnoted that a delay in communicating changes might have played a role in Apple’s case. While the law (a revision of the Telecommunications Business Act) took effect in March, Apple didn’t notify developers until late June. Google alerted Android developers in November of last year.

Both companies still take cuts from purchases made using alternative billing systems — they just take smaller portions. When Google announced its policy change, it maintained that it needed fees to “continue to invest” in Android and the Play Store. It’s not clear if these policies play any role in the investigation, however.

We’ve asked Apple and Google for comment. In a statement to Reuters, Google said it would continue cooperating with the KCC and that it had “worked closely” with both the government and developers to comply with the law.

The law allows for fines as high as two percent of the average yearly revenue for related business. Officials didn’t set expectations for possible fines, but the stores are major money generators. Apple, for example, paid developers $60 billion worldwide in 2021 and made a tidy profit for itself through fees on those sales. Even if South Korea only considered revenue earned within its borders to be actionable for fines, this could still lead to steep penalties if the KCC finds any violations.