At the end of February, the House of Representatives passed a budget calling for up to $4.5 trillion in tax cuts over 10 years.

Now, the haggling begins.

Many of the tax cuts from the 2017 tax bill, which passed during President Trump’s first term, are set to expire at the end of this year. He wants them renewed, and Congress has shown little appetite for crossing him.

Extending those provisions would eat up most of that $4.5 trillion, and on the campaign trail, Mr. Trump floated many additional ideas for tax cuts that would cost a lot of money. Few are likely to come to pass.

Still, strange things happen to tax bills in the dead of night. You never know what changes aides could make in the hours before a vote, without much of Congress seeing them.

These are the things to watch for.

Provisions From Previous Bills That Are Set to Expire at the End of 2025

Tax Brackets

The 2017 tax law reset — and lowered — the percentage of income that most people pay in federal income taxes. You can see where you stand currently on the Internal Revenue Service’s website; the Tax Foundation’s website has a 2017 table, which uses dollar figures that are not adjusted for the inflation that has occurred since then.

If no new bill is passed to extend these cuts, the percentages will revert to where they were in 2017, with new income bands in each tax bracket.