The Senate Budget Committee Tuesday passed S.1, known as the Tax Cuts and Jobs Act, by a party line, 12-11 vote.  The full chamber voted 52-48 Wednesday evening to begin debate Thursday morning, clearing the way for a full Senate vote late Friday or early Saturday morning.

The full chamber vote was a procedural step opening up a formal debate session limited to 20 hours in which any Senator can offer unlimited amendments. A filibuster would be disallowed based on the “reconciliation” instructions within the bill, so-called because the bill “reconciles” yearly spending with revenue and spending legislation. After debate ends, a session known as a “vote-a-rama” occurs in which all proposed amendments receive votes. It is likely to end with an amendment by Republican leaders incorporating all the changes.

The tax bill is further subject to the Byrd Rule, named after Senator Robert Byrd and enacted in 1985 as an amendment to the Congressional Budget Act of 1974. The rule allows Senators during the reconciliation process to block legislation if it possibly would increase the federal deficit more than $1.5 trillion beyond ten years.

Conforming to the Byrd Rule has led to various ideas under discussion amongst Republican Senators regarding raising enough revenue to cover federal spending or cutting federal spending in conjunction with cutting taxes. Both options would require a “trigger” mechanism. If economic growth alone does not reconcile spending with raising revenue, the “trigger” mechanism would be enacted and either taxes would be raised some time in the ten-year period or spending would be cut. Entitlement spending cannot be substantially cut under reconciliation rules.

Senator Bob Corker said he has gotten assurances that such a provision to raise taxes based on a trigger would be inserted, but acknowledged that the provision may violate a Senate Budget Rule that says reconciliation bills cannot contain provisions that lack a fiscal effect. The Congressional Budget Office may be unable to analyze a provision based on a hypothetical level of future revenue. Senators James Lankford and Jeff Flake have supported a trigger mechanism while Senators Thom Tillis, Dean Heller and David Perdue have voiced their skepticism about it.

The bill would cut the corporate tax rate to 20 percent from 35 percent. It would make individual tax cuts temporary and create seven income tax brackets, with a bottom rate of 10 percent and a top marginal rate of 38.5 percent, down from the current rate of 39.6 percent. As it stands, it also eliminates the state and local tax deduction.

Senators Marco Rubio and Mike Lee have said they will offer an amendment to expand the child tax credit and make it refundable against a family’s payroll tax liability. The amendment calls for increasing the corporate tax rate to 22 percent from 20 percent to pay for such an expansion. It would also make the child tax credit available to families with higher incomes.

Senator Steve Daines said an agreement has been reached with Senator Ron Johnson and others to raise the deduction for so-called pass-through business, such as LLCs and S Corporations, which pass their income on to their owners, to 20 percent from 17.4 percent. He also said a tax provision has been agreed upon that would allow U.S. domestic companies that have export sales to foreign customers to reduce their tax burden.

Senator Susan Collins has said she will offer amendments on the Senate floor, including one to make $10,000 of property taxes deductible. She indicated Thursday morning that her support for the bill would depend on passage of the amendment as well as an agreement she struck with Republican leaders to separately pass two health-care bills designed to stabilize the individual insurance market. Those bills are aimed at offsetting the impact of repealing the individual mandate in the Affordable Care Act.

A provision to open the Arctic National Wildlife Refuge to oil drilling is expected to be included based on a request from Senator Lisa Murkowski, though committee staff members have been working to tweak the provision to comply with parliamentary rules meant to exclude provisions that are not primarily fiscal in nature.

If the bill passes the full chamber later tonight or tomorrow, the House and Senate would then need to reconcile their tax plans in conference.