In the context of preferential trade agreements, Rules of Origin have attracted negative attention for their propensity to serve protectionist objectives. Against this background, the author seeks to shed light on several conceptual and practical challenges in connection with the Rules of Origin negotiated in the EU-UK Trade and Cooperation Agreement. The discussion proceeds from two basic propositions: first, the Rules of Origin included in this agreement resemble, in essential terms, those included in other modern EU trade agreements with advanced-economy partners; and second, preferential Rules of Origin, such as those agreed between the EU and the UK, embody the outcome of reconciling the divergent interests of import-competing and export industries by the negotiating partners. The author has identified and analysed the following specific challenges posed by the Rules of Origin in the EU-UK Trade and Cooperation Agreement: (1) limited possibilities for origin cumulation; (2) protectionist potential of transitional origin requirements and origin quotas; (3) trade-hindering effect with respect to Northern Ireland; and (4) chilling effect of the potential review of inward processing schemes on trade. Based on the analysis conducted, the author concludes that these challenges negatively affect trade because they operate to foreclose the expansion of legitimate trade opportunities under the EU-UK Trade and Cooperation Agreement. Origin, Rules of Origin, Preferential Origin, Free Trade Agreements, EU-UK Trade and Cooperation Agreement, Brexit, Inward Processing, Returned Goods, Diagonal Cumulation, Origin Quotas