The Charity Commission has published guidance on how it conducts investigations and how the trustees of charities under investigation should behave.
The commission recently expressed concern about a lack of cooperation from trustees during some recent cases. A spokeswoman said there was no connection between those cases and the new guidance.
The guidance will be sent to all charities that are investigated in future in order to help them understand what the process will involve. Separate documents cover statutory inquiries, which are opened when the commission needs to use its statutory powers, and lower-risk regulatory compliance cases.
Andrew Hind, chief executive of the commission, said trustees needed to be "absolutely clear from the outset" about their responsibilities during an investigation.
"The behaviour and level of cooperation of trustees during some investigations has fallen well below what we would expect, given the seriousness of the concerns at stake," he said. "I hope this guidance will reinforce the importance of charities under investigation engaging seriously with the commission."