Sue Ryder Care is extending its customer loyalty card nationwide after successful trials.
"We got three results from the pilots," said Alan Hodges, director of retail at Sue Ryder Care. "We generated more interest in our shops, we increased our donor base and it put several points on our sales."
The card entitles customers to save towards a £5 discount on donated goods. In return, they are asked if Sue Ryder Care can add their details to its fundraising database.
"We also have a questionnaire on the back of the application leaflet that allows us to better understand what our customers do and do not want," he added.
The scheme has aroused criticism from high-street retailers, which say charity shops undercut them.
A spokesman for the Forum of Private Businesses said: "When charity shops start embarking on more commercial practices, they should be subject to the same taxes and conditions as independent retailers."