I received a substantial overpayment of a guaranteed bonus in February 2008 that was not detected until March of this year (2009). I do not have the money to repay my employer who has suggested that I repay it immediately on a pretax basis. They have suggested that I will then get a credit against my 2009 taxes. To complicate matters, the original incorrect payment was related to a distribution of shares in October 2007 that are now worthless. What are my obligations to repay? Am I responsible for their error?