This article examines imports by Swedish firms and the utilization of the tariff preferences offered by the EU-South Korea Free Trade Agreement. To benefit from tariff preferences, the importer must make a formal request to use the preferences and also document the origin of the imported products (with a certificate of origin provided by the foreign exporter). This may be costly, and some importers choose to pay import tariffs even when tariff preferences are available. Hence, the preferences are not fully utilized. Using a detailed firm-transaction level data set on Swedish imports from South Korea, we analyse the determinants of preference utilization and how firms learn to use preferences. The results show that preference utilization is strongly correlated with potential duty savings, which depend on the preference margin and the size of the import transaction. From a learning perspective, we find that preference utilization is closely related to the number of import transactions undertaken by the firm, suggesting a learning-by-doing mechanism. The length of time the firm has been involved in importing activities plays a smaller role.