Treasury’s Book-Tax Guidance Comes Down on Business’s Side

The Treasury Department signaled it’s putting its thumb on the scale in big business’s favor over the corporate book-income tax, easing up on how tough the tax should be on companies.

Treasury said Wednesday it would make business-friendly changes in how companies’ research costs are treated under the 15% corporate alternative minimum tax. That move, and several other changes to CAMT rules announced in a notice Wednesday, make it clear that President Donald Trump’s Treasury is using the regulatory process to soften the tax’s impact on business, some practitioners and tax-advocacy groups said.

Wednesday’s guidance is “notable not just for ...