Cape Town - Finance Minister Pravin Gordhan anticipates revenue collection will be R5bn less this year than his February estimate.
In his 2012 medium-term budget policy statement, tabled in parliament on Thursday, he said this was based on projected weakness in the economic environment, with R3.9bn less tax expected from "persons and individuals", and R1.7bn less expected from companies.
"If economic conditions deteriorate, or mining sector output is disrupted over an extended period, further downward revision may be warranted," Gordhan warned.
However, tax revenue would be 10.6% higher than last year.
"Gross tax revenue collection is expected to remain subdued next year, but should improve during the outer years of the medium-term expenditure framework period as economic conditions strengthen," Gordhan said.
Mineral and petroleum royalties had been revised downward due to lower commodity prices and mining strikes.
VAT and customs duties collections had been revised upwards.