In a typical treasury office the morning ritual still involves opening a spreadsheet that shows the next month’s interest cost. That spreadsheet has, until now, been fed by JIBAR, the Johannesburg Interbank Average Rate, a forward-looking benchmark that tells you the rate you will pay weeks in advance.
On Moneyweb host Simon Brown heard from Yushavia Ramlall, chief operating officer at Intengo Market, that the Reserve Bank is replacing JIBAR with ZARONIA, the South African Rand Overnight Index Average. Unlike JIBAR, ZARONIA is a backward-looking rate: it is calculated from the actual overnight rates that occur each day and compounded over the period. The final rate is therefore only known a few days before a payment is due.
For a three-month loan that used JIBAR, a treasury team would have received four data points over a twelve-month span. Under ZARONIA the same contract will generate 365 data points. That increase in frequency sounds technical, but it changes the whole forecasting process. Companies now have to estimate interest expense later, adjust accruals on the fly and ensure that daily rate ingestion is reliable.
Why the “spreadsheet trap” matters
Ramlall warned that the danger is not the spreadsheet itself, most finance professionals rely on them daily, but the governance around a single, often undocumented, model. When a major funding obligation depends on a spreadsheet that only one person understands, the risk of error or oversight rises sharply. The new benchmark forces organisations to ask: can we demonstrate where the benchmark data came from, what controls were applied, and whether the process can be repeated consistently?
The Reserve Bank has set 31 December as the cut-off date. That leaves just over 90 days for firms to stress-test their end-to-end workflow, from data ingestion to final payment. According to the podcast, some organisations have already converted a few instruments, but many still lack a clear picture of their JIBAR-linked exposure, which totals roughly R43 trillion domestically and over R100 trillion offshore.
For small and medium enterprises that borrow in rand-linked contracts, the impact is tangible. A change in the timing of rate certainty can affect cash-flow forecasts, loan covenants and the ability to meet debt service on schedule. Companies that have robust treasury systems and documented controls will navigate the transition with minimal disruption. Those that rely on ad-hoc spreadsheets may need to invest in new software, update policies and train staff quickly.
Ramlall’s advice is clear: start by mapping every JIBAR-linked exposure, then run a full process test that includes data capture, calculation and approval steps. If any link in that chain cannot be demonstrated, the organisation is not ready for ZARONIA and should prioritise remediation before the deadline.
While the Reserve Bank’s move aims to reduce reliance on a single reference rate and improve market transparency, the real test will be how quickly firms can adapt their internal controls. The transition is less about a new number and more about a new discipline in treasury operations.
For further reading on the benchmark reform, see the South African Reserve Bank website. More analysis on how the change affects corporate finance can be found in our Markets & Finance section.
Treasury teams outside the largest banks and corporates should note that JIBAR-linked exposure is not limited to obvious loan products: interest rate swaps, floating-rate bonds and even some supplier financing arrangements can carry embedded JIBAR references that are easy to overlook in a manual inventory, which is part of why Ramlall’s advice to map every exposure systematically, rather than relying on institutional memory of which contracts matter, is worth taking literally rather than as a general caution.
