Treasury Secretary Steven Mnuchin on Sunday refused to explain how President Donald Trump will support his claim that he won’t personally benefit from the outlined tax proposal the White House released last week.

“How are Americans going to know if the President gets this benefit if he doesn’t release his tax returns?” George Stephanopoulos asked Mnuchin on ABC News’ “This Week,” referring to part of the proposed policy that would cut taxes on certain high-earning businesses that currently pay individual rates.

“That’s just not fair, because, again, we haven’t published the rules as to what’s going to apply to the pass-through rates, so you’re making certain assumptions that I don’t think are correct,” Mnuchin replied.

“I wouldn’t need to make the assumptions if we had the President’s tax returns,” Stephanopoulos said. “The President himself has said publicly he’s not going to get a benefit from this tax plan. My question to you is, how are the American people going to know that if he’s not releasing his tax returns?”

“I think the American public will be comfortable with the information they have,” Mnuchin said. “We’re going to make sure that there’s the proper rules. There’s going to be full transparency, as we go through the legislative process, what those rules are so that rich people can’t take advantage of it.”

Office of Management and Budget Director Mick Mulvaney on Sunday had a different explanation for why he could not provide a more specific defense of the Republican plan: It isn’t finished yet.

“I’ve seen the criticisms, and all I can tell you is that no one can make real detailed analysis of the plan yet,” Mulvaney said. “Because it’s not finished.”