Software exporter Patni Computer Systems would have to take up additional burden of up to $ 33 million, following a review of tax liabilities of its US operations."The company currently estimates that it will record additional tax and other related liabilities in the range of $ 23-33 million as a result of review and restatement process for 2001-05," Patni CFO Deepak Sugani said.Part of these liabilities would be stated in the results of FY04 and between $ 4-14 million will be recorded in the company's results of the quarter ended June 30, 2006, he said.With such a big burden falling on it, the company is might go in for a appeal against the IRS demand, Sugani said.The liability of Patni is because of the demand raised by US Internal Revenue Service after a review of the company's books for the years 2001-04.IRS had started with the tax review of the company's US operations for the years 2001 and 2002 and expanded it to cover 2003 and 2004."The review in respect of years 2001 and 2002 is close to completion while the review of 2003 and 2004 is yet to start," Sugani said.As a result of that review process, the company is re-assessing its obligations for corporate taxes, payroll and related taxes, interest and related expenses for the years 2001-2005, Patni said.