Candidates hoping to earn a spot as Donald Trump’s running mate are reportedly expected to submit their tax returns to the campaign, even though the presumptive GOP nominee has said he has no immediate plans to make his own taxes public.

NBC’s Katy Tur reported Wednesday that all vice presidential hopefuls would be required to submit their returns as a standard part of the vetting process. Citing an anonymous source within the Trump campaign, Tur also reported there would be no “litmus test” for prospective candidates on any specific issue. Instead, their comprehensive beliefs and personal backgrounds would be taken into consideration, she said.

When pressed about whether VP candidates would have to hand over their taxes, former presidential candidate Ben Carson, who assisted with Trump’s search, told MSNBC’s Chuck Todd on Tuesday that the campaign was following “normal” procedure.

“I would say that the normal vetting procedures would be under way, all the things that are normally asked for,” Carson said. “Nothing outside the normal.”

Trump’s own announcement that he may not release his tax returns during the campaign breaks with decades of historical precedent for presidential candidates. He promised to make his taxes available as soon as as the IRS completes a “routine audit” of his finances.

There is no legal requirement preventing Trump from releasing the returns while he is being audited, and embattled former President Richard Nixon made his public while under audit in the midst of the Watergate investigation.