A debt payable on demand becomes 'due' for purposes of prescription under section 12(1) of the Prescription Act 68 of 1969 when the loan is advanced, unless the parties clearly and unequivocally intend to defer the date when the debt becomes due. In ordinary commercial loan agreements, a clause providing that the loan is repayable within a specified period after written demand is a procedural term relating to mora (placing the debtor in default), not a suspensive condition or time clause that defers when the debt becomes 'due'. Such a clause does not delay the commencement of prescription. The creditor's right to claim repayment arises immediately upon advance of the loan, even though the debtor may have a period after demand to make actual payment. Prescription therefore begins to run from when the debt arises (upon advance), not from when demand is made. For parties to successfully defer prescription until demand, there must be clear contextual indicators beyond standard wording that this was their intention - such as special relationships between parties, unusual circumstances, or express provisions to that effect.