Audit regulators have seen enough altered documentation lately that they felt the need to formally remind auditors that doctoring work papers is a no-no.

The Public Company Accounting Oversight Board published a staff audit practice alert indicating its inspectors have seen cases even at firms affiliated with the global networks where auditors are adding to or altering audit files and passing off the alterations as original documentation. “Evidence identified in connection with certain recent oversight activities has heightened the staff’s concern about such misconduct,” the PCAOB wrote in its alert.

The PCAOB says its inspection rules require audit firms and all their associated individuals to cooperate with the board in regulatory inspections. “This duty to cooperate includes an obligation not to provide improperly altered documents or misleading information in connection with the board’s inspection process,” the alert says. Audit standards on documentation also come into play, the PCAOB points out, and they make no provision for adding to or altering an audit file after the fact.

The board says it has issued enforcement orders in past cases where it found improper documentation or lack of cooperation with inspections. In certain recent cases, the board says it has seen instances where documents were created shortly before or during a PCAOB inspection, then made available to inspectors as if they’d been in the audit file all along. “These recent instances involve both domestic firms and non-U.S. firms, including members of global networks,”

The PCAOB is urging anyone with information about altered documentation to report it either directly to to the board’s inspection or enforcement staff, or to its tip center. The board also says tipsters, “in appropriate circumstances,” can utilize their firm’s internal whistleblower and complaint systems. “Voluntary and timely self-reporting of violative conduct, including violations of the obligation to cooperate with Board inspections or investigations, may be a factor in determining whether to impose sanctions against a firm or person and what sanctions to impose,” the PCAOB wrote.