Work out the prescribed-rate interest a late-paying client owes you.
For sole proprietors and small contractors staring at an overdue invoice. Applies the Prescribed Rate of Interest Act 55 of 1975 to a B2B debt.
Sound familiar?
- “A client agreed 30-day terms and is now 60 days past due.”
- “You're not sure what rate of interest you're allowed to claim under SA law.”
- “You want a clean figure to put on a letter of demand.”
What this tool does
Calculates simple interest at the current prescribed rate (10.5% p.a., pinned 2026-05-29) on an overdue invoice for the number of days between the due date and the date paid. Adds it to the outstanding amount to give the total owed.
Prescribed rate: 10.5% per year · pinned 2026-05-29
Repo rate plus 3.5 percentage points. The rate moves with the repo rate: confirm the current prescribed rate before relying on a calculation.
Defaults to today.
What the law actually says
- •Prescribed Rate of Interest Act 55 of 1975 sets the rate that applies to a debt where no other rate is agreed.
- •The Minister of Justice gazettes the rate as the repo rate plus 3.5 percentage points (Government Notice R6668 of 2025 basis). The rate MOVES with the repo rate, so always confirm the current rate before relying on a figure.
- •South Africa has no equivalent of the UK Late Payment Act fixed-compensation fees: only interest and (if proven) actual recovery costs are recoverable.