The government has named businesses that did not pay some staff the minimum wage.
The official list includes Northern Ireland businesses, horse racing trainers Alan King and Lucinda Russell, and retailer B&Q.
Those named will have to repay the money owed to staff.
Separately, new figures suggest that wages are falling behind in real terms.
That is a warning about household budgets.
Prices are increasing at a faster rate than earnings, leaving workers with lower real incomes.
The government list and the pay data together underline financial strain for workers.
Officials said further steps would follow for employers that underpaid workers.