On a month-on-month basis, consumer inflation was at 0.4% in April compared to 1.0% the previous month.
Analysts polled had predicted April inflation of 7.0% year on year and 0.5% month on month.
The inflation figures come a day before the central bank is due to announce its latest interest-rate decision.
The South African Reserve Bank (Sarb) has hiked interest rates nine times in a row since November 2021 to try to tame inflation.
Analysts predict the Sarb will raise its repo rate by another 25 basis points to 8.00%, but financial markets have been pricing in a larger rate hike.
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