Because Boxing Day falls on a Sunday, thousands of retail staff who choose to work will be paid standard Sunday rates rather than a Bank Holiday premium.
Sainsbury's confirmed that its store workers would be paid the usual Sunday premium on Boxing Day, with the usual Bank Holiday premiums on 27 and 28 December.
Asda said 105 of its stores would be open on Boxing Day, with workers getting time-and-a-half.
Morrisons, meanwhile, said it had not yet made public its opening schedule over Christmas. No one from Tesco was available for comment.