The company, which is 80 percent owned by resources giant Anglo American PLC, issued its 2012 full-year results on Monday.
Amplats said it lost production of some 305,600 ounces of platinum due to an eight-week strike that crippled its operation in Rustenburg.
The loss compared with a profit of nearly R8 billion in 2011.
In January, Amplats said it would close some operations, sell one mine in South Africa and cut 14,000 jobs.
That decision has pushed platinum prices higher and triggered stinging backlash from the South African government and the ruling African National Congress.
Amplats is currently consulting with stakeholders, including unions and government departments, over its plans but says the restructuring is needed to save the business.
"While we are not pleased with the operational and financial performance, it is important to put things in context. Operationally, 2012 was a challenging year for Anglo American Platinum and the platinum industry as a whole," said Chris Griffith, Amplats' chief executive.
"The year was characterised by lower prices, illegal industrial action which impacted production, unit cost, labour productivity and, of course, profitability and earnings."
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