The overall number of restatements filed by public companies fell in 2012, but the largest U.S. companies registered a second year of distinct increase in the number of cases where companies needed to restate their financial statements.

Across all public companies, restatements fell from 820 in 2011 to 768 in 2012, according to the latest data from research firm Audit Analytics. Restatements peaked in 2007 at 1,213, but fell to 922 the following year and have fluctuated from 715 in 2009 to the 2011 high of 820.

Among U.S. accelerated filers, however, or those with market capitalizations of at least $75 million, restatements have increased for a second year straight. Accelerated filers accounted for 158 restatements in 2010, then rose to 202 in 2011 and 245 in 2012, according to the data. Last year, Audit Analytics flagged increases in restatements for companies according to their listings, noting increases for companies trading over the counter, where more mistakes might be expected, and on the New York Stock Exchange.

According to the research firm's assessment of restatements, the severity of the mistakes that led to restatements and the negative consequences they cause also also diminished in 2012 by every measure used to assess the data. That includes the direct effect on earnings, the average cumulative effect on earnings per restatement, the percentage of restatements that had no effect on earnings, the average span of time covered by restatements, and the average number of issues that led to restatements.

The biggest restatement in 2012 came from JPMorgan Chase, which adjusted earnings by $459 million in mid-2012 when it discovered a problem with the valuation of certain positions in the synthetic credit portfolio of the firm's chief investment office. JPMorgan said it discovered information suggesting its traders marks were not acceptable, so it remarked the positions using external mid-market benchmarks, adjusted for liquidity.

Among restatements in 2012, the largest number, or 15 percent, were filed because of problems with debt, quasi-debt, warrants, and equity security issues. The next largest batch, or 14.6 percent arose because of problems with tax issues. Cash flow statement classification errors accounted for the third most common cause for restatements. Revenue recognition came in fifth on the list of problems.

Audit Analytics has been tracking restatement data since 2001, collecting more than 12,000 restatements or non-reliance filings from more than 7,000 public companies.