These companies will be hit hardest by GOP tax reform

The Republican Party's planned border-adjusted tax is an elegant solution for supporting domestic exporting industries, but paying for it will require a huge tax hike on companies that import their wares.

Cowen Research published a report Thursday that estimates the effect of the reform plan, and other planned measures, like eliminating the deductibility of interest and a headline corporate tax cut, on different industries and companies. Here are some of the big-name firms Cowen says will be hurt by reform:

1. Apple: The world's largest company would see its tax bill jump because it won't be able to deduct the expense of assembly abroad.
2. Constellation Brands: The largest beer importer in America will not be able to expense the cost of goods it brings across the border, like its Corona brand.
3. Gap: Between 50% and 80% of the retailer's cost of the goods its sells comes from abroad.
4. Walmart: Walmart's low margins means that it may not be able to survive a tax hike on imported goods without raising prices.
5. Target: Will suffer from the same conundrum as Walmart, but will be worse off since less of its revenue comes from domestically-sourced groceries.
6. J.C. Penney: The department store has high debt loads, and interest on debt will not be deductible under the Republican plan.

Why it matters: These are just a few of the many companies whose earnings will come under assault by the GOP plan. Don't expect them to sit idly by.