Congress is debating the biggest rewrite of U.S. partnership rules in 60 years, which may lead to higher taxes for real estate and finance businesses or prompt them to restructure operations to avoid new costs.

The more dramatic of two options from Dave Camp, the top Republican tax writer in Congress, would remove some of the flexibility that has made partnerships attractive legal structures for real estate investors and hedge funds. He also offered an alternative with lesser changes to simplify some rules and leave the core of the current system in place.

The broader proposal surprised tax law specialists, who hadn't anticipated a major policy shift for the 3.2 million U.S. partnerships. The plan may alter existing arrangements by making it more difficult to allocate income and property among partners without triggering tax consequences. Lawyers said they have spent the past week scouring Representative Camp's draft bill, especially his new second option.