Though Sprint had a year-long formal SEC investigation from 2012-2013, there appears no SEC investigative activity as of Feb-2014, the date of the SEC's most recent letter to us regarding the company.  We've not previously researched T-Mobile but did find signs of SEC investigative activity in the past concerning MetroPCS, a unit it acquired in May-2013.

Our Search History:  Sprint

Sprint had an SEC investigation lasting just over one year, starting June 2012 and ending July 2013.  Documents show the matter started as an informal probe on 12-Jun-2012 and became a formal investigation only six weeks later, on 25-Jul-2012.  Subpoenas were served on both the company and its auditor, KPMG. That investigation was completed a year later, on 02-Jul-2013. 

In Nov-2012 and Jul-2013, our access to records on Sprint was blocked, due to this investigation. 

In response to our Dec-2013 request on Sprint, on 11-Feb-2014, the SEC provided us copies of the correspondence, formal order, and subpoenas pertaining to the 2012-2013 investigation of Sprint.

Our Search History:  T-Mobile

We've conducted no research on T-Mobile specifically.  However, it appears there was some kind of investigative activity in the past two years involving MetroPCS, but we do not know its nature. 

In Jul-2012 the SEC reported finding no records responsive to our request on MetroPCS.  That changed in Jun-2013, when the SEC blocked our access to records over concern their release could potentially interfere with law enforcement activities.  The SEC again blocked our access to records, same reason cited, in Mar-2014. Most recent data from the SEC, dated May-2014, suggests there is nothing recently active in SEC files on MetroPCS. 

As a reminder, in 2012 Deutsche Telekom agreed to acquire MetroPCS via a reverse merger and combine it with T-Mobile USA. In May 2013, T-Mobile USA completed the MetroPCS acquisition.

Documents of Note: 

We have 113 pages of records related to the 2012-2013 investigation of Sprint. Included are copies of the SEC's letters initiating the informal inquiry in Jun-2012, it's formal order of investigation dated Jul-2012, subpoenas dated that same period, and the letter sent to indicate completion of the investigation on 02-Jul-2013.