The Charity Commission has been criticised for failing to amend its model memorandum and articles for charitable companies until little more than a week before new guidance is due to be implemented.
The Companies Act introduces new company registration rules on 1 October, which include changes to clarify questions on conflicts of interests and directors' benefits.
Andy Ball, who is setting up a second-tier organisation in Kent, said he had been waiting months for the commission's new model memorandum and articles so that he could avoid following out-of-date guidance.
"It's shameful that the commission is still promoting the old model documents on its website," he said. "I feel sorry for those who have downloaded the old versions, and who might shortly have them rejected by Companies House."
The new model was published on the Charity Commission's website on 18 September.
A commission spokeswoman said: "We said that we would make this available ahead of the change and that is what we have done."