The case relates to the dominance of Google's Android operating system, which is one of the world's most popular mobile software systems, competing fiercely against Apple's iOS. The Android OS controls more than 80 percent of smartphones globally.
The EU has scrutinized that dominance, arguing that Google should look to make competition fairer and allow smaller players in the market to flourish. It is widely expected to fine the firm a record levy on Wednesday.
According to the Wall Street Journal, that fine will amount to 4.34 billion euros ($5.06 billion). The Journal, citing an official familiar with the matter, said the decision is not expected to be discussed at a meeting between EU Competition Commissioner Margrethe Vestager and other officials.
Shares of Alphabet, Google's parent company, shed more than 1 percent during U.S. premarket trading.