OBJECTIVE: To assess the contribution of different food groups to total salt purchases and to evaluate the estimated reduction in salt purchases if mandatory maximum salt limits in South African legislation were being complied with. DESIGN: This study conducted a cross-sectional analysis of purchasing data from Discovery Vitality members. Data were linked to the South African FoodSwitch database to determine the salt content of each food product purchased. Food category and total annual salt purchases were determined by summing salt content (kg) per each unit purchased across a whole year. Reductions in annual salt purchases were estimated by applying legislated maximum limits to product salt content. SETTING: South Africa. PARTICIPANTS: The study utilised purchasing data from 344 161 households, members of Discovery Vitality, collected for a whole year between January and December 2018. RESULTS: Vitality members purchased R12·8 billion worth of food products in 2018, representing 9562 products from which 264 583 kg of salt was purchased. The main contributors to salt purchases were bread and bakery products (23·3 %); meat and meat products (19 %); dairy (12·2 %); sauces, dressings, spreads and dips (11·8 %); and convenience foods (8·7 %). The projected total quantity of salt that would be purchased after implementation of the salt legislation was 250 346 kg, a reduction of 5·4 % from 2018 levels. CONCLUSIONS: A projected reduction in salt purchases of 5·4 % from 2018 levels suggests that meeting the mandatory maximum salt limits in South Africa will make a meaningful contribution to reducing salt purchases.