Wal-Mart Stores Inc. plans to cut thousands of back-office positions around the country, a sign that the retailer’s effort to make its cavernous stores more efficient is also changing the face of its workforce.

The largest private employer in the U.S. is eliminating about 7,000 store accounting and invoicing positions over the next several months. The jobs are mostly held by long-term employees, often some of the highest paid hourly workers in stores. The retailer wants those employees working with shoppers, not in backrooms,...