The CRA believes that a tax adviser should takes steps to ensure their clients correct past errors (I01-1R2 (February 17, 2026), paras. 116-117), but neither the Income Tax Act nor the Excise Tax Act impose such a duty. Other statutes do require taxpayers to correct past errors. From this, the authors conclude that Parliament intended not to impose such a duty for income tax or HST purposes. Failing to correct past errors, if they were not the result of negligence, should not attract criminal or civil penalties or permit the CRA to reassess beyond the normal reassessment period.
Is a lawyer in Ontario required by the Rules of Professional Conduct to advise a client to fix past errors? The authors suggest the Rules do not impose such an obligation, but they have not researched the issue in depth.
David M. Sherman and Balaji (Bal) Katlai “Is a Taxpayer Required To Correct a Past Error?” Tax for the Owner-Manager 26:2 (April 2026)
