你说超过10年不能再调整tax filing, 如属实there is nothing you can do...

unless CRA regulations provide exceptions. But for the same reason I doubt CRA can collect back taxes you owed more than 10 years ago. You first received CRA collection letter two years ago which was beyond the 10 year prescribed period to collect, if Canada has such 10 year "statute of limitation".  最好去consult a competent tax lawyer to deal with the matter. Tax issues are no laughing matter.