At 1553 GMT, the rand traded at 18.7425 against the dollar, 0.6% stronger than its previous close after firming 1% earlier.

"The rand has seen some mild strength recently, with the Medium-Term Budget Policy Statement (MTBPS) due out tomorrow, and available data on the fiscal half year showing that expenditure is at 51% of the budget estimate," said Investec chief economist Annabel Bishop in a research note.

The main economic event in South Africa will be Wednesday's MTBPS, which updates economic forecasts, adjusts the budget and makes emergency changes to spending.

"Markets and the credit rating agencies will be watching the debt projections, with downgrades a risk on markedly higher debt revisions," Bishop added.

Shares on the Johannesburg Stock Exchange fell, with the blue-chip Top-40 index closing about 0.6% lower.

Revenue service figures earlier showed South Africa recorded a trade surplus of 13.14 billion rand ($701.96 million) in September.

South Africa's benchmark 2030 government bond was stronger, the yield down 3 basis points at 10.675%.

($1 = 18.7189 rand)

(Reporting by Anait Miridzhanian and Bhargav Acharya; Editing by Mrigank Dhaniwala and Ken Ferris)