Failed companies left combined debts worth 584.43 billion yen in May, up 72.9 percent from the previous month, credit research agency Teikoku Databank said Tuesday.
The agency said, however, that corporate bankruptcies had only risen a slight 1.5 percent to 614 cases since April.
The average debt left by insolvent companies came to 952 million yen, up 70.3 percent. The figures are part of the agency's report on companies with debt of 10 million yen or more that have filed for legal bankruptcy status.
In a change to its monthly reports, Teikoku Databank said it would start excluding companies that have become virtually insolvent but not filed for bankruptcy. The change starts with the reporting month.
Due to the growing availability of private-sector services for aiding corporate revival, companies are increasingly receiving debt waivers upon insolvency, and many of those that opt not to file for legal bankruptcy can no longer be viewed as having gone belly up, it said.