A final version of the big GOP tax bill is expected to be released today (Friday).
The House-Senate conference committee has been working hard to mesh competing tax plans.
Uncertainty has surrounded the bill which President Trump hopes to get approved by Christmas.
Florida Senator Marco Rubio said Thursday he'll vote no unless the legislation makes the child tax credit more generous.
"I've been pretty consistent in my communications on this issue and that is I want us to see the refundable portion of the child tax credit increased from its current number," Rubio told reporters on Capitol Hill on Thursday. "If it stays at $1,100, I'm a 'no.' Let's hope it doesn't."
Several other Republican senators remain undecided.