Senate Republicans’ $1.5 trillion tax cut would not pay for itself, according to a report released on Thursday by the nonpartisan Joint Committee on Taxation. The report is a significant setback for Republicans, who have asserted that the tax cuts would grow the economy enough to cover the cost of the plan.

Source Estimated cost of Senate tax plan Cost including estimated effect of economic growth Joint Committee on Taxation $1.63 trillion $1 trillion Penn Wharton Budget Model $1.64 trillion $1.39 trillion Tax Foundation $1.78 trillion $516 billion Penn Wharton Budget Model, Sources: Joint Committee on Taxation The Tax Foundation . Note: Most estimates are 10-year revenue effects without factoring in government spending, known as outlays. However, the J.C.T.’s only estimate of the bill’s effects with economic growth, shown above, includes outlays.

The report of the committee, Congress’s official tax scorekeeper, is the latest in a number of analyses that have found that the cuts could add a significant chunk to federal budget deficits, a move that would seem counter to years of Republican criticism of the deficits accumulated under the Obama administration.

In the Congressional Budget Office’s analysis of the Senate tax bill, the cuts would add $1.414 trillion to the deficit by 2027. That estimate does not include the amount that would be offset by the economic growth spurred by tax cuts.

The Senate Bill’s Cumulative Cost Without Economic Growth $1.5 trillion 1 0.5 0 2018 2020 2022 2024 2026 $1.5 trillion 1 0.5 0 2018 2020 2022 2024 2026

Some Senate Republicans have expressed concerns about the bill’s deficits. Senator Bob Corker of Tennessee pushed to include in the final legislation some kind of safeguard that would trigger automatic tax increases or spending cuts if economic growth fails to cover the cost. But the provision was determined to run afoul of budget rules by the Senate parliamentarian on Thursday.

Will the Tax Cut Pay for Itself?

In a 2018 budget blueprint passed by Congress, lawmakers allowed enough room to lose about $1.5 trillion in revenue, but Republicans have said that the proposed tax legislation is designed to “pay for itself.”

How Much the Tax Plan Could Add to the Deficit $10.1 trillion Projected deficits over the next 10 years under current law $1.5 trillion Cost of tax cuts proposed by Congress $10.1 trillion Projected deficits over the next 10 years under current law $1.5 trillion Cost of tax cuts proposed by Congress

They have argued that economic growth spurred by the cuts would make up for the difference in tax revenue, eventually reducing the deficits. But there is no consensus among economists about the amount of growth that would occur, and few estimate that the bill would generate enough economic growth to offset the drop in tax revenue.

To measure the macroeconomic effects of the Senate tax plan, economists have calculated estimates both with and without factoring in economic growth caused by the cuts. The results are produced using varying economic assumptions and show a wide range of estimated costs.

For the Senate version of the tax plan, estimates vary widely across the Joint Committee on Taxation, the University of Pennsylvania’s Penn Wharton Budget Model and the conservative Tax Foundation, whose models tend to assume large growth effects. But all three analyses show that even when factoring in economic growth, the tax bill would not pay for itself.

Senate Bill Cost including economic growth Estimated cost of plan REVENUE neutral J.C.T. Tax Foundation Wharton –$2 trillion -1.8 -1.6 -1.4 -1.2 -1 trillion -0.8 -0.6 -0.4 -0.2 0 Cost including economic growth Estimated cost of plan REVENUE neutral J.C.T. Tax Foundation Wharton –$2 trillion -1.6 -1.2 -0.8 -0.4 0 Cost including economic growth Estimated cost of plan J.C.T. Tax Foundation Wharton –$2 trillion -1.6 -1.2 -0.8 -0.4 0

Estimates for the House version of the plan, which passed with 227 Republican “yes” votes on Nov. 16, also vary widely, but each shows the bill would cost more than $1 trillion even when accounting for economic growth. The Joint Committee on Taxation has not released an estimate for the House version that includes economic growth effects.

House Bill Cost including economic growth Estimated cost of plan REVENUE neutral Tax Foundation Wharton J.C.T. –$2 trillion -1.8 -1.6 -1.4 -1.2 -1 trillion -0.8 -0.6 -0.4 -0.2 0 Cost incuding economic growth Estimated cost of plan REVENUE neutral Tax Foundation Wharton J.C.T. –$2 trillion -1.6 -1.2 -0.8 -0.4 0 Cost including economic growth Estimated cost of plan Tax Foundation Wharton J.C.T. –$2 trillion -1.6 -1.2 -0.8 -0.4 0