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Due diligence defence (occupational health and safety)

The due diligence defence, as the Canadian Centre for Occupational Health and Safety describes it, lets a person charged under occupational health and safety legislation be found not guilty by proving that all reasonable precautions were taken. In Ontario, s.66(3) of the Occupational Health and Safety Act sets it out for certain listed provisions.

An owner who is charged with a safety offence may need to show what the business did to prevent harm. The Canadian Centre for Occupational Health and Safety says due diligence is important as a legal defence for a person charged under occupational health and safety legislation, and that the defendant must be able to prove that all reasonable precautions were taken to protect workers.

Ontario’s wording

Section 66(3) of Ontario’s Act applies on a prosecution for failure to comply with s.23(1), clause 25(1)(b), (c) or (d), or s.27(1). It says it is a defence for the accused to prove that every precaution reasonable in the circumstances was taken. The accused carries that burden of proof. Read the whole of s.66 before relying on it.

What a buyer can ask

  • What written programs, training and inspection records the seller can produce.
  • Whether any charge or investigation is open, and which provisions it concerns.
  • Which of those records will transfer with the business.

Sources

This definition is checked against primary sources. Links were last confirmed on the dates shown.

  1. 01
    Government of Ontario (e-Laws)Government
    Occupational Health and Safety Act, R.S.O. 1990, c. O.1
    ontario.ca·Checked Oct 24, 2026
  2. 02
    Canadian Centre for Occupational Health and Safety (CCOHS)Government
    Health and Safety Legislation in Canada - Due Diligence
    ccohs.ca·Checked Oct 25, 2026
  3. 03
    Canadian Centre for Occupational Health and Safety (CCOHS)Government
    Health and Safety Legislation in Canada - Introduction
    ccohs.ca·Checked Oct 24, 2026

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