The figure was contained in a written response to the Public Administration Select Committee from Dame Suzi Leather, former chair of the commission, after her appearance before the committee in July.
The response contained further information on matters discussed during the hearing and was published on the parliamentary website last week.
"For clarity, the commission did not pay any other parties’ costs in the litigation," it said, and stated that the legal costs on the commission’s side were £185,000.
In the response, Leather said it was not possible to provide a figure for the regulator’s internal administrative costs on the case. "We require our staff who carry out preparation and support work for the tribunal appeal hearings to work flexibly and, when not working on appeal cases, they have other legal advisory and case duties," she said.
"This flexible approach, together with the fact we do not operate a charging system for our legal services, means we do not maintain a time-recording system."
The hearing, which took place in May 2011, considered the commission’s public-benefit guidance on charitable fee-charging schools after a judicial review application from the ISC and a reference by Dominic Grieve, the Attorney General, who asked for clarification of how charity law should operate in relation to fee-charging independent schools.
The tribunal ruled that key parts of the commission’s guidance was wrong and should be redrafted. The regulator has since withdrawn the guidance and it is being updated.
A spokeswoman for the commission said it had "sought counsel's advice as part of our revision of our public benefit guidance, but obviously that remains ongoing and we won't be able to say what the costs of this have been until the process has concluded".
In her response, Leather said the commission "was under a duty to assist the tribunal in the clarification of the law by its participation in the legal proceedings".
"As the committee will know, although the guidance was held to be wrong with regard to its regulatory emphasis, fundamental aspects of charity law put forward by the commission and which the commission had relied upon, namely that a charity cannot be constituted or operate in a way which excludes the poor, were upheld," the response said.
"In our view, the commission carried through an important element in public service in assisting the tribunal to clarify the law, and that is our justification for our engagement."