An intention to waive must be inferred reasonably; no-one can be presumed to have waived rights without clear proof. The test for such intention is objective. Silence and inaction will do when a positive duty to act or speak arises.

A security company rendered security services to a municipality for six years. During the second phase it submitted invoices which were disputed by the City. The company then submitted new invoices based on the City’s calculations. It disagreed with those calculations but did not communicate its disagreement to the City.

By accepting the City’s calculations, the security company waived its rights to claim the balance. The debts became due as soon as the company raised and submitted invoices in accordance with the payment procedures prescribed in the contract. Therefore the claims had prescribed by the time action was instituted.

The case is Premier Attraction 300 CC t/a Premier Security v City of Cape Town.