In the UK, there is major economic change such as Brexit on the horizon. The impact of such change is likely to vary across UK regions. There is also a growing demand for improved regional economic analysis to help inform devolution and City Deal-type policymaking. Despite these concerns, there are no comprehensive national statistics on interregional trade in the UK. This paper fills this gap, proposing a framework for estimating interregional trade between the devolved nations of the UK: England, Scotland, Wales, and Northern Ireland. We explain where gaps exist in the current UK data landscape and suggests various ways in which these could be addressed. We then apply our framework using currently available data, presenting initial results for trade between the 4 nations of the UK in 2015. Recommendations for future work are also presented, including the need to evaluate current methods for collecting trade information within the UK.