Mispricing of international trade in natural resources contributes to significant tax base erosion from developing countries but is difficult to measure using aggregate trade statistics. In this paper, we apply a novel approach motivated by legal rules for trade and transfer mispricing to estimate abnormal pricing in gold and cocoa exports from Ghana, i.e. exports valued outside an assumed arm's length price range that indicates fair market values. Using daily frequency, transaction-level data from Ghana Customs, our results indicate abnormally undervalued exports of gold and cocoa from Ghana equalled USD 8.8 billion in constant prices (base year 2011) or USD 4.1 billion in current prices between 2011 and 17. Approximately 11% of gold doré exports, 1% of cocoa bean exports and 7.2% of cocoa paste exports appear abnormally undervalued. The implied corporate tax base erosion equals USD 2.2 billion in constant prices (base year 2011) corresponding to an average annual decrease of 0.3% in Ghana's tax-to-GDP ratio.