Spain is not playing around with tech billionaire Elon Musk. Spain’s stock market supervisor has fined Musk-owned social media platform X approximately $5.8 million (€5 million) for failing to make sure that a cryptoasset company that used X for advertisements had authorization to provide investment services.

“(CNMV has decided to) impose a fine on Twitter International Unlimited Company… for failing to fulfil its duties to verify whether Quantum AI was authorized to provide investment services by the CNMV and whether Quantum AI was included in the list of entities warned about by the CNMV or by foreign supervisory bodies,” the document said.

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The fine, dated Nov. 3, was published in Spain’s official bulletin on Thursday.

The penalty stemmed from X failing to ensure that a crypto advertiser Quantum AI, was properly authorized to provide investment services and was not on any warning lists issued by Spanish or foreign regulators. Spain has strengthened its rules in recent years to prevent misleading crypto promotions and to make sure online platforms verify advertisers and clearly communicate investment risks to the public.

The fine highlights the growing regulatory scrutiny faced by social media platforms as channels for financial advertising. While X has the right to appeal the decision in Spain’s high court, the case underscores the legal obligations that platforms now face under global digital, financial, and advertising regulations. It also signals to investors and tech companies that regulators are increasingly enforcing compliance measures to protect consumers in emerging, high-risk markets like cryptocurrency.

X, formerly known as Twitter, is the social media platform owned by Musk. He rebranded it as X following his 2022 acquisition and later integrated it with his AI firm, xAI, in an all-stock deal in March 2025. The transaction valued X at roughly $33 billion, excluding about $12 billion in debt.

In 2025, X has seen a modest rebound in advertising revenue, with U.S. ad sales up around 17.5% year-on-year and global ad revenue rising approximately 16.5%. The platform remains a central hub for news, public commentary, and AI-driven features, reflecting Musk’s push toward integrating advanced AI tools into social media.

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Despite growth, X faces regulatory challenges. European authorities are scrutinizing its operations, including a fine in Spain for crypto-asset advertising violations and an ongoing investigation in Ireland under the EU Digital Services Act. User metrics and financial disclosures remain partly opaque, so reported valuations and revenue figures should be interpreted with caution. These caveats highlight the uncertainty in assessing X’s long-term stability and profitability.

Musk’s dual role as owner of both X and xAI amplifies the spotlight, as regulators and the public closely monitor how AI tools and advertising practices intersect with financial markets.