Raymond Chirwa, RBCT's chief operations officer, said in a statement contractors on the 1.2 billion rand ($148.5 million) project could work double shifts to ensure the project was ready for commissioning in time for the new date.
"On-site contractors will consider using additional resources to meet the extended commissioning date," he said.
Chirwa said a risk assessment to establish the completion date showed the Phase V expansion project to expand the 72 million tonne RBCT would not be ready by July 1 as expected.
He said the delay was due to the contractor experiencing technical challenges with some equipment that has to be installed as part of the expansion project.
In December, Chirwa said the end of the project had been put off by three months to July 1 due to technical difficulties.
Chirwa had said there was enough coal in South Africa and enough demand to justify the expansion, at least through the next decade.
The expansion would also cater for emerging black owned coal exporters.
The export terminal has been operating at less than its present capacity due to constraints on the rail network which transports the coal from the mines to the port.
South Africa is one of the world's major coal exporters, but regular train derailments and delays along the Richards Bay coal line have dented business confidence in freight logistics group Transnet's [TRAN.UL] ability to meet international commitments.
Analysts say if Transnet does not deliver soon, the terminal could still be exporting around 60 million tonnes of coal despite the expanded export capacity.
RBCT shareholders include miners Anglo American (AGLJ.J), BHP Billiton (BILJ.J), Xstrata (XTA.L), petrochemicals group Sasol (SOLJ.J) and diversified mining group Exxaro (EXXJ.J).