Reza Motazedi told Third Sector that the Sofa, which is a requirement of the Sorp accounting standard, was the best means for charities to quantify their public benefit credentials.
"Trustees need to link the information in their annual reports to the data given in the Sofa," he said.
"In my opinion, the problem isn't so much about charities proving that they are providing public benefit. It is more about sending the message out in a positive way."
A Charity Commission spokeswoman said that although the Sofa provided a category to explain the costs of charitable activities, the annual report was the best place to give an account of a charity's public benefit.