The Shifren principle: a golden goose or an ugly duckling?

In SA Sentrale Ko-op Graanmaatskappy Bpk v Shifren the lease said it could be varied only in writing. A later oral arrangement, including a cession of the right to sublet, did not move the written contract. The principle has been called a straitjacket ever since. It has also been the reason commercial parties can rely on the page they signed.

Almost every commercial agreement now carries the clause. It stops one side from rewriting the deal in a call. Both parties have to sign the change. Obligations that are not in the document are not in the deal.

The practical advice is dull and correct: if the commercial position has moved, write the addendum and have it signed. A memory of what was agreed on the phone will not survive the clause.