Also known as a MAC clause.

In the context of the acquisition of a target company or business, a contractual term in the acquisition agreement giving the buyer the right to withdraw from the transaction if certain events occur between exchanging the acquisition agreement and completion that are detrimental to the target, its business or assets. MAC clauses are used in both public takeovers and private acquisitions. For further information, see Practice note, Material adverse change (MAC) clauses: acquisitions.

In the context of lending transactions, a clause which acts as a "catch all" provision that aims to allow the lender to call a default if there is an adverse change in the borrower's position or circumstances (for example, a large negative variation shown in successive financial statements of the borrower). MAC clauses are a common feature of facility agreements. Although they are always heavily negotiated, MAC clauses are not commonly used to default a borrower. For further information, see Practice note, Material adverse change (MAC) clauses in finance documents.