DETROIT — General Motors Corp. posted a company record $39 billion loss in the third quarter, as a charge involving unused tax credits brought an abrupt end to string of three profitable quarters for the nation’s largest automaker.

The loss reported today was one of the biggest quarterly corporate deficits ever and it sent GM’s shares down more than 8% in premarket trading.

The loss was attributed to a $38.6 billion noncash charge largely related to establishing a valuation allowance against accumulated deferred tax credits in America, Canada, and Germany, as well as mortgage losses at GM’s former financial arm, GMAC Financial Services.

But accounting rules require that companies expecting to keep losing money cannot keep carrying deferred tax credits indefinitely and must write down the value of such credits.

The net loss amounted to $68.85 a share, compared with a net loss of $147 million, or 26 cents a share, in the third quarter of last year.

The results included a $3.5 billion after-tax gain on the $5.4 billion sale of Allison Transmission in August.

Without special items, the company reported a $1.6 billion loss, or $2.80 a share.

The company reported record third-quarter automotive revenue of $43.1 billion and record global sales for the quarter of 2.39 million cars and trucks.

But the automaker continued to lose money in its home market, North America, where it reported a net loss from continuing operations of $38.2 billion for the quarter including the noncash charge. That compares with a net loss of $667 million in the year-ago period.

Without the charge, the company’s North American loss was $247 million in the third quarter of 2007.

“We continue to implement the key elements of our North America turnaround strategy, and these initiatives are driving steady improvement in our financial results, despite challenging North America market conditions,” GM Chairman and Chief Executive Rick Wagoner said in a statement.