MAC Clause (Material Adverse Change)

A Material Adverse Change (MAC) clause — sometimes called a Material Adverse Effect (MAE) clause — is a provision in a purchase agreement that allows a buyer to withdraw from a transaction, without penalty, if a significant adverse change in the business occurs between the signing of the agreement and the closing date. MAC clauses serve as a buyer's contractual escape hatch for events that materially impair the value of what they agreed to purchase.

In Canadian mid-market transactions, the gap between signing and closing typically runs 30–120 days, during which the business continues to operate. If a major customer cancels, a key employee departs, a regulatory issue emerges, or operating results deteriorate significantly, the buyer may invoke the MAC clause to exit. What constitutes a "material" change is intentionally left somewhat ambiguous in most agreements — it is a negotiated concept, and disputes about whether a MAC has occurred are among the more contentious issues in M&A litigation.

Sellers negotiate to narrow the scope of the MAC definition by excluding events that are systemic (affecting the entire industry or economy) rather than specific to the business, excluding changes in general market conditions, and excluding results of the sale process itself becoming public. Buyers negotiate to keep the definition broad and to include any decline in earnings above a specified threshold. The MAC clause is distinct from the conditions precedent — it is typically invoked after the initial conditions are satisfied, to address deterioration during the pre-closing period.

See also: Purchase Agreement, Conditions Precedent, Closing, Letter of Intent.