ECONOMICS Working Paper Series No. 09-2021 Trade Data Statistics Michael Gasiorek and Nicolò Tamberi University of Sussex Business School m.gasiorek@sussex.ac.uk | n.tamberi@sussex.ac.uk Abstract: The UK-EU Trade and Cooperation Agreement (TCA) entered into force in January 2021. At the same time, the collection method for UK-EU trade statistics changed, moving from Intrastat to customs declarations. As a result, the gap between UK reported exports to the EU and their mirror flows reported by the EU widened substantially. Imports are not affected as the UK will not change theh collection method before 2022. This considerable difference in UK exports casts doubts on which dataset should be used to analyse the effects of the TCA on UK-EU trade, whether UK or EU reported data. After reviewing the methodological changes, we believe that the change from country of consignment to country of origin in EU imports declarations represents the main break in the series. We advise analysts and researchers to use HMRC reported exports flows instead of their EU reported mirror flows. Comparison of data by country of origin and consignment and comparisons of trade flows with freight traffic data confirm our beliefs. JEL codes: F14; Y10 Key words: UK-EU trade statistics; Trade and Cooperation Agreement