Brussels said Facebook "deliberately or carelessly" submitted deceiving data, breaking EU merger rules.
The world's greatest informal organization confronts fines of up to 1 for every penny of yearly deals or generally $125m, as indicated by Facebook's yearly income in 2014.
She said: "Our auspicious and compelling survey of mergers relies on upon the precision of the data gave by the organizations included. In this particular case, the Commission's preparatory view is that Facebook gave us inaccurate or misdirecting data amid the examination concerning its procurement of WhatsApp. Facebook now has the chance to react."
Facebook will have until January 31 to react to the European Commission.
The issue respects a WhatsApp security strategy change in August in which it said it would impart a few clients' telephone numbers to parent organization Facebook, activating examinations by various EU information insurance powers.
Clients of the moment flag-bearer were given the capacity to quit sending data to Facebook through settings in WhatsApp's applications on cell phones.
The Commission said Facebook had swore in its notice of the securing that it would not join the client bases of the two organizations' to ease rivalry concerns.
European information assurance bunch G29 formally communicated its worries toward the end of October.
"In today's Statement of Objections, the Commission takes the preparatory view that, in spite of Facebook's announcements and answer amid the merger audit, the specialized probability of consequently coordinating Facebook clients' IDs with WhatsApp clients' IDs as of now existed in 2014," it said.
Facebook said that it had acted in "accordance with some basic honesty" amid the procedure.
"We regard the Commission's procedure and are sure that a full survey of the realities will affirm Facebook has acted in compliance with common decency," a representative for the organization said.