Introduction
In commercial contracts, the issue of late payment interest is often addressed by referencing established financial benchmarks. These benchmarks—such as SOFR, EURIBOR, prime lending rates, or statutory rates like South Africa’s “mora interest”—serve as the foundation for calculating interest owed on overdue amounts. The choice of benchmark can significantly impact the enforceability, fairness, and practicality of a contract, depending on the legal jurisdiction and the commercial context. Understanding the strengths and limitations of each option is essential for contract drafters and negotiators seeking to protect their interests while ensuring compliance with relevant laws and market practices.
Common Benchmarks for Late Payment Interest
| Benchmark | Definition | Pros | Cons |
| LIBOR (London Interbank Offered Rate) (phased out) | Historically used as a global cost-of-money reference. | Widely recognized and understood. Reflected international borrowing costs. | Discontinued (synthetic LIBOR only temporarily available). Risk of unenforceability in new contracts. Manipulation scandals undermined credibility. |
| SOFR (Secured Overnight Financing Rate) | Replacement for USD LIBOR, based on repo transactions secured by U.S. Treasuries. | Transparent, transaction-based. Regulator-endorsed replacement. Less prone to manipulation. | Backward-looking (overnight rate, compounded for term). May not align with commercial cash flow needs. Less intuitive for non-financial parties. |
| EURIBOR (Euro Interbank Offered Rate) | Benchmark for euro-denominated contracts. | Widely used in EU. Reflects European market conditions. Familiar to multinational businesses. | Subject to regulatory oversight and periodic reform. Can be volatile in crises. |
| Prime Lending Rate (Bank Prime Rate) | Rate banks charge their most creditworthy customers. | Easy to understand. Directly linked to domestic lending environment. Common in U.S. and South Africa. | Can be higher than interbank rates. May fluctuate with central bank policy, creating unpredictability. |
| Statutory “Mora Interest” (South Africa) | Prescribed Rate of Interest Act: Repo Rate + 3.5%. | Legally recognized default if no rate agreed. Provides certainty and enforceability. Aligns with central bank policy. | Fixed at time of default (not floating). May not reflect actual cost of funds. Less flexible for commercial negotiation. |
| Fixed Contractual Rate (e.g., 8% p.a.) | Explicitly agreed rate in contract. | Simple, predictable. Avoids disputes over benchmarks. Easy to administer. | May be unenforceable if deemed excessive (“penalty interest”). Can become outdated if market rates shift significantly. |
Key Considerations for Choosing a Benchmark
- Jurisdictional enforceability: Courts may strike down excessive or vague rates. Statutory defaults (like mora interest) provide a safety net.
- Commercial fairness: Rates should balance deterrence against late payment with fairness to counterparties.
- Market alignment: Using floating benchmarks (SOFR, EURIBOR, prime) ensures rates track economic conditions.
- Administrative simplicity: Fixed rates are easier to apply but risk being misaligned with market reality.
Risks & Practical Tips
- LIBOR legacy clauses: Contracts still referencing LIBOR risk uncertainty; parties should amend to SOFR or other recognized rates.
- Penalty clauses: Excessive fixed rates may be unenforceable as punitive rather than compensatory.
- Cross-border contracts: Align benchmarks with the currency and jurisdiction of payment obligations to avoid mismatches.
- Grace periods: Including a short grace period (5–10 days) fosters goodwill and reduces disputes.
Bottom Line
For South African contracts, the safest fallback is the statutory mora interest (Repo + 3.5%), while internationally SOFR and EURIBOR are the most credible replacements for LIBOR. Fixed rates remain practical but must be carefully calibrated to avoid being struck down as penalties.
References
- https://www.traverssmith.com/knowledge/knowledge-container/references-to-libor-in-late-payment-clauses-mind-the-gap/
- https://www.svsattorneys.co.za/post/understanding-mora-interest-in-south-africa
Disclaimer
This information is provided for general guidance only and does not constitute legal advice. The application and enforceability of late payment interest rates, including statutory “mora interest,” may vary depending on the specific facts, contract terms, and jurisdiction. Parties should consult a qualified legal professional for advice tailored to their particular circumstances before relying on any benchmark or statutory rate in commercial agreements.