The Securities and Exchange Commission has been writing Tesla some strongly worded letters about its accounting practices.
The regulator criticized Tesla for using "individually tailored" measurements in its August earnings release, according to a series of letters between Tesla and the SEC reported by The Wall Street Journal.
The regulator has been cracking down on the use of non-GAAP information in earnings releases, the report said.
The SEC letters also criticized Tesla for failing to make a "substantive case" for using non-GAAP figures. An expert consulted by the Journal noted the strong language of the letters.
Tesla announced in early October that it would stop reporting non-GAAP figures. The company had previously defended their use by saying non-GAAP figures better reflected their finances.
Tesla did not return a request for comment.