KKR is getting unusually pointed criticism from some of its public-pension fund investors, after they discovered that KKR didn’t tell them for almost a year that its decision to refund some money was prompted by a regulatory exam.

The contretemps, rare in the tightly-controlled world of private equity, stems from a Securities and Exchange Commission exam of the industry giant in late 2013. Regulators found that the firm had erroneously charged some expenses and didn't fully disclose it was collecting certain fees, according to a document obtained from one of KKR's largest investors, the Washington State Investment Board.