CLOCS-2 is an observational, retrospective case-control study that investigates whether or not everyday loyalty card use in high street retailers can help identify early signs of cancer. The cancer types in focus are bladder, bowel (also known as colon/colorectal), endometrial, liver, oesophageal, ovarian, pancreatic, stomach, uterine and vulval. CLOCS-2 is using a case-control design to compare purchasing patterns of participants with (cases) and without (controls) these cancer types diagnose in order to potentially develop a way to detect cancer earlier. The study aims to include participants with and without cancer across the United Kingdom who use loyalty cards at two high street retailers. The CLOCS team will analyse past purchasing behaviour from about 1,500 participants (750 cancer cases and 750 controls) in the United Kingdom utilising information already collected through their use of loyalty cards.