The FCC is expected to announce the proposed fines totaling upwards of $200 million on AT&T Inc, Verizon Communications Inc, Sprint Corp and T-Mobile US Inc on Friday.
If confirmed, this will mark some of the highest penalties the FCC has ever imposed on firms and the first time it has taken action against companies over the issue of trading customer location data.
The four companies allegedly sold access to the data for marketing purposes and services like bank fraud protection, despite pledging publicly that they wouldn't.
FCC Chairman Ajit Pai confirmed in January that 'one or more wireless carriers apparently violated federal law.'
The FCC and the carriers did not immediately comment.
The scandal began when the FCC announced back in May 2018 it was investigating reports that a website flaw could have allowed the location of mobile phone customers to be tracked.
That probe expanded into other uses of consumers' location data by third-party firms.
It came to light that carriers had allowed the use of location data for programs like roadside assistance, logistics, medical emergency alert services, human trafficking alerts and fraud prevention.