Because of his efforts to overturn the 2020 election, Rudolph W. Giuliani has been indicted in two states and hit with a $148 million defamation judgment that forced him to seek bankruptcy protection.

Through all of that, he has kept a reliable financial ally: a charity founded to honor the memory of a firefighter killed on Sept. 11, 2001. The problem, according to his creditors’ lawyers, is that he has withheld that detail throughout his first five months of bankruptcy proceedings.

In a filing last week, attorneys for Mr. Giuliani said that one of the former New York City mayor’s companies, Giuliani Communications, receives about $16,300 per month in income from his one-man internet show “America’s Mayor Live.” Mr. Giuliani’s attorney said that money comes “mainly” from the Sept. 11 charity, the Stephen Siller Tunnel to Towers Foundation.

The revelation of the revenue stream comes after months of deeply contentious arguments from creditors about the state of Mr. Giuliani’s personal finances, with complaints that much of it remains deliberately incomplete and opaque. Only recently did creditors learn, through social media, that Mr. Giuliani had a contract to earn money from a new branded coffee line.

The Tunnel to Towers Foundation confirmed that it sponsored both the livestream and Mr. Giuliani’s now-canceled radio show. The group declined to say how much it paid overall.