Tokyo-based Toshiba's unaudited results showed it racked up a 532.5 billion yen (USD 4.8 billion) loss for the April- December 2016 period.
In February, the company, whose products include computer chips and household appliances, had forecast a 390 billion yen (USD 3.5 billion) loss for the fiscal year.
Its auditor, PricewaterhouseCoopers Aarata, said it could not reach a conclusion in its review of the figures because of uncertainties related to the acquisition of US nuclear construction company CB&I Stone and Webster.
Costs soared after the March 2011 nuclear disaster in Fukushima, because of growing safety concerns and stricter regulations.
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A souring of sentiment toward nuclear power in some countries, weaker oil prices and the growing appeal of natural gas have also hurt its nuclear energy-based business strategy.
Meanwhile, the company's reputation has been tarnished by a scandal over doctoring of accounting books to meet unrealistic profit targets.
Toshiba still faces the challenge of decommissioning the Fukushima Dai-ichi nuclear plant, which sank into multiple meltdowns after the 2011 tsunami in northeastern Japan.