you are right, Peter. Sure you can report to IRS. But when there is no capital gain or capital gain is less than your exemption amount, you don't have to report. You will know it if you have done tax filing with TurboTax or other tax filing software. Only if you do have a net capital gain after exemption, you have to report. The 2 years of use in 5 years tax rule is not set in stone. It allows you to prorate exemption based on your years of use. For example, if you only used 1 year in last 5 years, you will still get some exemption, may be half of 250000. If you use tax return software, it will calculate for you.