One Republican proposal to cut taxes could actually slash the earnings of big U.S. retailers by making it far more expensive to import goods into the country for sale.

The border-adjusted tax proposal aims to help keep jobs in the U.S. by making it more expensive for retailers to import goods, and if passed it will do a number on Walmart, Costco, Genuine Parts and Dick’s Sporting Goods, the Wall Street Journal reports. RBC Capital Markets said six large U.S. retailers could lose almost $13B in earnings should the tax plan go through, forcing retailers to raise prices to offset the loss.

But the plan isn’t all bad news for corporate retailers — the proposal would also cut the corporate tax rate and let multinational firms bring back stashed offshore profits while immediately writing off capital expenses. [WSJ]