Whether the tax refund is taxable to you depends on whether you itemized deductions in the year you paid the property tax or relied on the standard deduction. If you took the standard deduction, the refund is not taxable to you. If you itemized, you have to determine the extent to which the deduction for the property tax payment reduced your taxes; some or all of the refund may be taxable now (on the return for the year in which the refund was received). You don’t have to amend your 2008 return.
An IRS examination of your tax return, generally limited to a three-year period after you file.