keep records for at least 3 years of tax returns and related receipts. If
audited, the IRS reserves the right to review tax returns filed during what is
known as the 'period of limitations' which is generally the past 3 years from
the date you filed your most recent tax returns.
Buying an electronic/hybrid car to make it taxable, you must buy it new for your own use. And you must have a total tax liability of at least $7500 in year, if it is less than that, you lose the rest of the credit.