Party leaders insist that there are no showstopping differences between their two bills, each of which features a decrease in the corporate tax rate from 35 percent to 20 percent. Still, the bills feature differences worth hundreds of billions of dollars.

Lawmakers are expecting an intense period of work starting Monday as lobbyists descend on the conference committee that will negotiate differences between the two pieces of legislation. Of particular concern will be changes made hours before the Senate passed its final legislation early Saturday morning, when the Senate changed its bill to preserve a provision of the current tax code that sets an alternative minimum tax floor for very wealthy individuals. That provision would be eliminated in the House bill, and scrapping the alternative minimum tax has long been a priority for GOP tax writers…

The most delicate discussions will probably take place over how to tax so-called “pass-through” businesses. There are millions of these firms in the United States, and they can range from small businesses to large real estate companies and professional sports franchises. They are often owned by a single entity or partnership, and their income is passed through to the owners, who pay taxes on that money through the individual income tax code.