The Senate relies on its parliamentarian to advise it on what provisions in a law are strictly budgetary in nature and which would have only an incidental impact on the budget. The latter are not allowed to be included in a reconciliation bill, which requires only 50 votes to pass.

"It now seems less likely that the Senate will be able to debate the [Trump tax bill] and pass it prior to July 4," Spencer Perlman, director of healthcare research at Veda Partners, wrote in a Thursday client note.

Perlman added that the ruling also makes it more likely that any legislation that passes "may be less detrimental to hospitals than feared," as it would keep more Americans on the Medicaid rolls.