If you’re going to mess with the IRS, you should probably make sure you’ve paid your taxes first. That’s the moral you can extract from the tale of Warren Buffet’s private aircraft company, NetJets Inc, so far. In November 2011, NetJets, owned by Buffet’s Berkshire Hathaway Inc., sued the Internal Revenue Service (IRS) for $642.7 million in allegedly illegally imposed ticket taxes and penalties. Now, four months later, the IRS is suing NetJets for $366.3 million in unpaid taxes.

The countersuit, filed in district court on Thursday, claims that four NetJets units have “failed, neglected or refused” to pay penalties and excise taxes between 2003 and 2009. NetJets Aviation Inc. owes the most, $302.1 million, NetJets International Inc. owes $53 million, Executive Jet Management Inc. owes $10 million and NetJets Large Aircraft Inc. owes $1.2 million, Thomson Reuters reports.

In his annual letter to Berkshire shareholders, released last month, Buffet wrote: “A few years ago NetJets was my number one worry: Its costs were far out of line with revenues, and cash was hemorrhaging. These problems are behind us.”