The Treasury Department could give companies retroactive relief from a 2017 tax law provision that may lead to many foreign subsidiaries being treated as more heavily taxed controlled foreign corporations.

Daniel McCall, IRS deputy associate chief counsel (International-Technical), said the government is working on proposed regulations and is considering requests that relief be retroactive. He also said that, short of retroactivity, the Internal Revenue Service could consider publishing the rules in “reliance” mode—meaning taxpayers could rely on the rules as proposed instead of having to wait for final regulations.

The timing question matters to companies with foreign subsidiaries that...