In 2016 we were jointly commissioned by UNISON and the TUC to undertake an analysis of over-indebtedness in Britain. The report highlighted how traditional measures of the debt burden understated this because they fail to take account of rising living costs. We construct a new measure based not on gross incomes but on the level of interest payments relative to the available surplus of income over non debt related expenditure. We call for this measure to be used to guide future policy interventions.