The CMA has contacted the three platform holders requesting information about their individual online contracts to obtain a better understanding of whether any action is necessary.
The UK non-ministerial government department has also requested for comments from users of any of the trio’s services to further assist in the investigation.
Outside of this, the firm’s term and conditions will be looked into alongside how each platform provider handles cancellations and refunds.
Roll-over contracts are becoming more and more commonplace and it's essential that they work well for customers, said CMA chief executive Andrea Conscelli.
“Our investigation will look into whether the biggest online gaming companies are being fair with their customers when they automatically renew their contracts, and whether people can easily cancel or get a refund.
“Should we find that the firms aren’t treating people fairly under consumer protection law, we are fully prepared to take action.”