The long, sorry saga of defunct online sportsbook BetOnSports continues to wind its way through the courts, as US tax authorities continue to pursue the nest egg of the site’s founder Gary Kaplan.

Law360 reported on a new brief filed this week in Eastern Pennsylvania federal court by Kaplan, the former boss of the Costa Rica-based BetOnSports, which went belly-up in 2006 after being targeted by US authorities for taking online sports wagers from American bettors.

The Internal Revenue Service (IRS) has long claimed that Kaplan owes the US government millions of dollars due to his failure to file tax returns for the years 2004 and 2005, during which time he sold $97m worth of shares in BetOnSports ahead of the company’s listing on the London exchange.

Kaplan sold his shares via two trusts based in the Isle of Jersey. In 2010, Kaplan settled the Kaplan Family Trust (KFT) and its underlying investment firm Nineveh Investments, under Bahamian law as a successor to the Jersey trusts. The Bahamas-based Equity Bank & Trust acts as the KFT’s trustee.