JJB Sports will pay a partial refund to customers who were overcharged for replica football shirts.
Which? said the retailer had agreed to pay up to £20 each for shirts bought between 2000 and 2001. It follows legal action by the consumer group on behalf of fans who between them bought nearly 1,000 football shirts.
Customers who joined the consumer group's case will get £20 from JJB Sports for each affected England and Manchester United shirt purchased during 2000 and 2001.
Fans who did not join the Which? case can still claim £10 per shirt by presenting either proof of purchase or the shirts themselves at a JJB store before February 5, 2009.
That action came after the Office of Fair Trading fined the retailer and nine other companies for fixing the price of England and Manchester United shirts during 2000 and 2001.
Which? started proceedings at the Competition Appeal Tribunal but agreed to settle out of court with JJB Sports.
The shirts were bought for up to £39.99 each for the adult sizes, Which? said.
Customers can claim a payment from JJB Sports even if they bought the replica shirts from Allsports Ltd, Blacks Leisure Group plc, Manchester United plc, Sports Soccer Ltd or JD Sports, according to the consumer group.
Under the terms of the agreement, JJB Sports will also pay the reasonable legal costs of the case, Which? said.
Customers claiming their payments at JJB stores must have a till receipt, credit card statement or bank statement showing proof of purchase during the relevant periods in 2000 and 2001. Fans who turn up with the shirts themselves will only get £5 if the label is missing.
Full details of the relevant shirts, their purchase dates, and how to claim the payments are available from Which? and JJB Sports.
The replica shirts affected by today's announcement are: Manchester United home shirts bought between June and October 2000; Manchester United centenary reversible shirts bought between June and August 2001; England home shirts bought between April and June 2000; and England away shirts bought between April and June 2000