Objectives To estimate the potential impacts of unmitigated and mitigated cost of living increases on real household income, mortality, and mortality inequalities in Scotland. Design Modelling study. Setting Scotland, 2022/23. Participants A representative sample of 5,602 Scottish respondents (within 2,704 households) in the 2015/16 Family Resources Survey. We estimated changes in real household income associated with differential price inflation (based on proportion of household spending on different goods and services, by income group), both with and without mitigating UK Government policies, and scaled these to the Scottish population. We estimated mortality effects using a cross-sectional relationship between household income and mortality data, by deprivation group. Interventions Baseline was Scotland in 2022/23 with the average wage and price inflation of preceding years. The comparison scenarios were unmitigated cost of living increases, and mitigation by the UK Government's Energy Price Guarantee (EPG) and Cost of Living Support payments. Main outcome measures Premature mortality rate and life expectancy at birth by Scottish Index of Multiple Deprivation (SIMD) group, and inequalities in both. Results Unmitigated price inflation was 14.9% for the highest income group and 22.9% for the lowest. UK Government policies partially mitigated impacts of the rising cost of living on real incomes, although households in the most deprived areas of Scotland would still be GBP1,400 per year worse off than at baseline. With the mitigating measures in place, premature mortality was estimated to increase by up to 6.4%, and life expectancy to decrease by up to 0.9%. Effects would be greater in more deprived areas, and inequalities would increase as a result. Conclusions Large and inequitable impacts on mortality in Scotland are predicted if real-terms income reductions are sustained. Progressive Cost of Living Support payments are not sufficient to offset the mortality impacts of the greater real income reductions in deprived areas.