OBJECTIVE: To determine if voluntary policies on supermarket checkout foods are associated with a difference in the healthfulness of foods displayed at, or near, supermarket checkout areas. DESIGN: Cross-sectional survey of foods at, or near, supermarket checkouts categorised as less healthy or not according to the Food Standards Agency's Nutrient Profiling Model. SETTING: One city in Eastern England (population about 125 000). SUBJECTS: All stores in nine supermarket groups open for business in June-July 2017 in the study city. Supermarket checkout food policies were categorised as clear and consistent, vague or inconsistent, or none. RESULTS: In thirty-three stores, 11 434 checkout food exposures were recorded, of which 8010 (70·1 %) were less healthy; and 2558 foods in areas near checkouts, of which 1769 (69·2 %) were less healthy. After adjusting for a marker of store size, the odds of a checkout food exposure being 'less healthy' was lower in stores with vague or inconsistent checkout policies (OR=0·63; 95 % CI 0·49, 0·80) and in stores with clear and consistent checkout policies (OR=0·33; 95 % CI 0·24, 0·45), compared with no policy. There was no difference in the odds of foods near, but not at, checkouts being less healthy according to checkout food policy. CONCLUSIONS: Supermarket checkout food policies were associated with lower odds of checkout foods but not foods near, but not at, checkouts being less healthy. Further research is required to explore impacts on purchasing and consumption.