Definition

Material adverse change (MAC)

A material adverse change clause allows a buyer to refuse to close if the business suffers a serious, adverse change between signing and closing. It exists because time passes between the two, and the buyer priced the business as it was when they signed.

Reviewed

MAC clauses are heavily negotiated and, in practice, hard to invoke. Courts have generally treated them as aimed at durable, fundamental deterioration rather than a bad quarter or a broad market downturn, and the party seeking to rely on one carries a heavy burden.

What is usually carved out

  • General economic, market or interest-rate conditions
  • Conditions affecting the whole industry rather than this business specifically
  • Changes in law or accounting standards
  • Effects caused by the transaction itself being announced

Sources

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

  1. 01
    Canada Revenue AgencyGovernment
    Selling a business
    canada.ca·Checked Aug 14, 2026
  2. 02
    Treadstone LawLegal commentary
    Material Adverse Change Clauses in Ontario Business Sale Agreements
    treadstonelaw.ca·Checked Aug 14, 2026
  3. 03
    Treadstone LawLegal commentary
    Conditions Precedent to Closing in an Ontario Business Sale Agreement
    treadstonelaw.ca·Checked Aug 14, 2026
  4. 04
    Treadstone LawLegal commentary
    Disclosure Schedules in an Ontario Business Sale Agreement
    treadstonelaw.ca·Checked Aug 14, 2026

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