Some Wal-Mart shoppers are eligible for a refund because the new Carpentersville supercenter overtaxed its customers.

From July 1-11, the store was mistakenly charging a sales tax rate of 9.5 percent rather than the village’s 9 percent rate, Carpentersville officials said. Wal-Mart representatives said the company took immediate action after learning of the error, and the sales tax rate was corrected July 12.

It is unknown how many customers were affected and how much money was over-collected, said Erica Jones, Wal-Mart senior manager of corporate communications.

The Wal-Mart Supercenter in Carpentersville, which relocated from an East Dundee location, held its grand opening June 22.

Company representatives said shoppers who were overtaxed can bring their receipts to the store at 365 Lake Marian Road for a refund. Some customers have already been reimbursed for the mistake, Jones said.

“It was totally a system error,” she said. “We apologize for it, and anyone who was overcharged will receive a full refund for the amount they were overcharged.”