The stock price plunged 9.45 per cent to 226.2 yen at one point after it surprised markets by saying its nine-month earnings report had "not yet become available".
The shares closed down 8.0 per cent at 229.8 yen.
"We have submitted a request to extend the deadline" by one month for the earnings which were due on Tuesday, Toshiba said in a statement, citing ongoing reviews by its lawyers and an independent auditing firm.
It was unclear if company executives would still hold a previously scheduled news briefing later in the day, according to a company spokeswoman.
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The sell-off extended morning losses that were sparked by a report in Japan's Nikkei business daily, which said Toshiba was going to issue a warning to shareholders that its future is in jeopardy.
Shares in the firm have almost halved since late December, when Toshiba first flagged huge losses in its atomic unit.
Earlier reports said Toshiba -- one of Japan's best-known firms and a cornerstone of its post-war industrial rise -- was likely to log a net loss of more than $4.0 billion in the April-December period.
The reported loss is related to problems with the value placed on a deal involving the purchase of a nuclear services company by Toshiba subsidiary Westinghouse Electric.
The Nikkei report said Toshiba's mounting losses would force the company to warn investors over its ability to continue as a going concern in its current form.
It would be the first such warning by the group since its birth from a 1939 merger, according to the Nikkei.
There is speculation Toshiba will dramatically reduce its nuclear operations and stop building new atomic power plants, but would continue designing and making reactors and other components.