Affirmative Portfolios CC v Transnet Limited t/a Metrorail

Affirmative Portfolios CC (appellant), a labour broker, entered into a tender arrangement with Transnet Limited t/a Metrorail (respondent) in November 1999 to supply 200 access controllers for station platforms. The tender was accepted on 29 March 2000 and a written agreement was signed in May 2000, stipulating a monthly rate of R358,800 (based on R15 per hour plus 15% administration fee, i.e. R17.25 per hour) for 36 months commencing 1 April 2000. The appellant had been providing services since September 1999. From April 2000, the appellant increased the charge to R17.25 per hour plus 15% administration fee (not the originally tendered R15 plus 15%), claiming that Transnet officials (Naicker and Mncube) had orally agreed to the increase. The respondent paid the increased rate without complaint from April to September 2000. At a December 2000 meeting, Transnet informed the appellant it had been overcharging and required reversion to the R15 per hour rate. The appellant reluctantly agreed but reserved its rights. In April 2002, Transnet terminated the agreement (later conceded to be unlawful). The appellant sued for underpayment, and Transnet counterclaimed for recovery of overpayments totaling R515,317.45 on grounds of unjustified enrichment.

• Whether the written agreement was validly varied by oral agreement, tacit agreement, or conduct to increase remuneration rates
• Whether the parol evidence rule precluded reliance on an alleged prior oral agreement
• Whether clause 10.1 (non-variation clause) was enforceable and prevented oral or tacit variation
• Whether written invoices signed by Transnet officials constituted sufficient written consent to vary rates
• Whether estoppel applied to prevent reliance on the non-variation clause
• Whether the condictio indebiti applied to recover overpayments
• Whether the requirement that the error must be excusable was satisfied in the counterclaim
• Whether the defence of non-enrichment applied

The appeal succeeded partially: (a) The appeal against the judgment on the appellant's claim of R833,660.87 was dismissed; (b) The appeal against the counterclaim was allowed; (c) The respondent was ordered to pay the costs of the appeal, including those occasioned by the employment of two counsel. The order of the court a quo was set aside and substituted with: (a) The plaintiff's claim for R883,660.87 is dismissed; (b) The defendant's counterclaim for R515,317.45 is dismissed; (c) Each party is to pay its own costs.

1. Where parties reduce their agreement to writing intending it to be the exclusive memorial of their transaction, the parol evidence rule prevents reliance on prior oral agreements that contradict or vary the written terms, particularly where the written agreement specifically addresses the subject matter in question (pricing). 2. A non-variation clause requiring prior written consent for any deviation is binding and enforceable. Such a clause cannot be varied orally or tacitly unless there is evidence that the parties agreed to delete or amend the clause itself. 3. Signed invoices or payment certificates do not constitute 'prior written consent' to vary contractual terms where a non-variation clause expressly requires such consent before any variation takes effect. 4. For the condictio indebiti to succeed, the payor's mistake must be excusable. Repeated failure over several months to check invoices against a readily accessible written agreement constitutes gross negligence or extreme slackness rendering the mistake inexcusable, particularly where no evidence explains why the error occurred or persisted. 5. The excusability of an error depends on all circumstances including: the relationship between parties, the defendant's conduct and whether it contributed to the error, the plaintiff's state of mind, and the culpability of the plaintiff's ignorance. Conduct so slack that it does not deserve the law's protection will not be excused as a matter of policy. 6. The defence of non-enrichment applies where the receiver has disposed of or lost part of what was paid, limiting liability to what remains at the time the action is instituted.

1. The Court acknowledged renewed academic calls to abolish the excusability requirement in the condictio indebiti (citing Daniel Visser's Unjustified Enrichment and Helen Scott's comparative article), but noted the present case was not appropriate for such a departure as the issue was neither raised nor argued by the parties. 2. The Court noted that the appellant could have availed itself of the equitable remedy of rectification if it was truly the common intention of parties that rates be varied, but chose not to do so. 3. The Court observed that the non-variation clause (clause 10.1) may itself be varied otherwise than in writing (citing Clemans v Russon Brothers (Pty) Ltd), but there was no evidence that parties applied their minds to deleting the clause. 4. Boruchowitz AJA reiterated (following Willis Faber and Bowman) that it is neither possible nor prudent to define exhaustively the circumstances in which an error can be excusable, and that much depends on context including the relationship between parties, the defendant's conduct, and whether the defendant was aware there was no debitum. 5. The Court noted that the excusability requirement admits of exceptions, particularly in cases involving payments made by persons in representative positions (such as executors in the Bowman case). 6. The judgment emphasized that whether conduct is inexcusably slack cannot be determined by rules of thumb, and conduct regarded as inexcusable in one case need not necessarily be so in others.

This case is significant in South African contract law and the law of unjustified enrichment for several reasons: 1. It reaffirms the strict application of the parol evidence rule and the binding nature of non-variation clauses in commercial contracts, particularly following formal tender processes. Parties cannot rely on alleged prior oral agreements that contradict written terms where the written agreement is intended as the complete memorial of the transaction. 2. It confirms that non-variation clauses requiring written consent are enforceable and cannot easily be circumvented by estoppel arguments, particularly in formal commercial relationships. 3. It represents an important application of the excusability requirement in the condictio indebiti, holding that repeated failure over several months to check invoices against a readily accessible written agreement constitutes inexcusable negligence, even where payments were made in error. 4. The judgment demonstrates that gross negligence or extreme slackness in conducting one's own affairs will defeat a claim for unjustified enrichment, regardless of whether the defendant induced the mistake. 5. It illustrates the continued application of the excusability principle despite academic calls for its abolition, while acknowledging the difficulty of defining what constitutes excusable error and the context-dependent nature of such determinations. 6. The case reinforces the defence of non-enrichment in unjustified enrichment claims, limiting recovery to what remains in the defendant's hands at the time of action.