The refunds for licensees were secured as a result of legal action earlier this year after they had been overcharged by PPL, but thousands have yet to claim money owed to them, it said.
A recent tribunal hearing showed that across eligible industries, 16,404 licensees have failed to claim refunds, and 5,027 of these are independent retailers.
ACS public affairs director Shane Brennan said one of the problems was that retailers were often confused by the music licensing system in the UK.
"Many retailers don't think the refund will amount to a lot of money, but actually they have been getting a substantial return from PPL," he said.
"Retailers should have received a letter saying that they are entitled to a refund, but my fear is that many may have thought this was junk mail and therefore not taken action. There is a sense it is not a major thing but really it is."
The accumulative value of refunds claimed by shops and stores so far is £4.1m.
"The legal victory to secure refunds for retailers has been a great success and that is why we are urging retailers to claim money owed to them," explained ACS chief executive James Lowman.
"The refund process has been made as light-touch as possible for retailers, with the onus on PPL to make contact. We recommend all retailers check if they have received notification for a refund and to submit this claim."