The rule for retaining tax returns and documents supporting the return is six years from the end of the tax year to which they apply. Your 2010 return and its supporting documents, for example, are safe to destroy at the en of 2016.
There are situations that alter this rule. If you have filed late returns, the six-year rule applies to date of filing, not the tax year.
“Objections and appeals and their expiry dates may go beyond the six-year guideline.” says Ben Campbell, certified financial planner with Investors Group Financial Services in Winnipeg, Manitoba. “Documents should be maintained until the last date of appeal expires, or the six-year period ends.
Use the last date as your guideline.”