As Senate Republicans release key details of President Donald Trump's spending package, some provisions, including the federal deduction for state and local taxes, known as SALT, remain in limbo.

Enacted via the Tax Cuts and Jobs Act, or TCJA, of 2017, there's currently a $10,000 limit on the SALT deduction through 2025. Before 2018, the tax break — including state and local income and property taxes — was unlimited for filers who itemized deductions. But the so-called alternative minimum tax reduced the benefit for some higher earners.

The Senate Finance Committee's proposed text released on Monday includes a $10,000 SALT deduction cap, which is expected to change during Senate-House negotiations on the spending package. That limit is down from the $40,000 cap approved by House Republicans in May.

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"SALT has been contentious for eight years," said Andrew Lautz, associate director for the Bipartisan Policy Center's economic policy program.

Since 2017, the SALT deduction cap has been a key issue for certain lawmakers in high-tax states like New York, New Jersey and California. These House members have leverage during negotiations amid a slim House Republican majority.

Under current law, filers who itemize tax breaks can't claim more than $10,000 for the SALT deduction, including married couples filing jointly, which is considered a "marriage penalty."

However, raising the SALT deduction cap has been controversial. If enacted, benefits would primarily flow to higher-income households, according to a May analysis from the Committee for a Responsible Federal Budget.

Currently, the vast majority of filers — roughly 90%, according to the latest IRS data — use the standard deduction and don't benefit from itemized tax breaks.

Plus, the 2017 SALT cap was enacted to help pay for other TCJA tax breaks, and some lawmakers support the lower limit for funding purposes.

In the Senate, "there isn't a high level of interest in doing anything on SALT," Senate Majority Leader John Thune said June 15 on "Fox News Sunday."

"I think at the end of the day, we'll find a landing spot, hopefully that will get the votes that we need in the House, a compromise position on the SALT issue," he said. 

But some House Republicans have already pushed back on the proposed $10,000 SALT deduction cap included in the Senate draft. 

Rep. Mike Lawler, R-N.Y., on Monday described the Senate proposed $10,000 SALT deduction limit as "DEAD ON ARRIVAL" in an X post.

Meanwhile, Rep. Nicole Malliotakis, R-N.Y., on Monday also posted about the $10,000 cap on X. She said the lower limit was "not only insulting but a slap in the face to the Republican districts that delivered our majority and trifecta."