The White House proposal to overhaul the U.S. food stamp program — and the deep cuts it would make to benefits for the poorest households — has sparked public outrage on both sides of the aisle. But there’s another change tucked into the proposal that businesses say caught them off guard — and could wind up costing them more than $2 billion.

That provision is a new fee that the White House wants to charge retailers that accept food stamps, which is now known as the Supplemental Nutrition Assistance Program.

The Office of Management and Budget said the fee would be assessed when stores sign up and would require renewal after five years. The budget office said the amount would depend on the size and type of retailer, but the president’s budget estimates that the fee would generate $2.4 billion in revenue over the next decade.

An OMB official described the fee as “modest” and “reasonable,” emphasizing that some large retailers redeem a billion dollars or more in food stamp benefits each year.

“Although a small number of stores may choose to leave the program rather than pay the fee, we do not expect that this will affect access to authorized stores,” the official said.

The proposal surprised the grocery industry, which is already fighting to block the controversial border adjustment tax on Capitol Hill. That measure would lower the cost of exports but raise the price of imports and has been widely opposed by chain retailers. Trump’s food stamp fee, however, would fall squarely on supermarkets.

Grocers oppose the “flawed policy of imposing fees on food retailers in order to reduce the cost of the federal government’s nutrition assistance benefits…