The aim of this study was to determine transparent food carbon footprint values for use in a climate tax, using a consistent methodology across the taxed food products and taking into account the need for such a tax to be administratively simple and accepted by affected stakeholders. Methods A method based on Life Cycle Assessment following the ISO 14067 standard was developed for establishing simplified, yet consistent and transparent, datasets on the carbon footprint of food, for use as a base in a climate tax on food. Several sensitivity analyses were carried out to test the effects of inevitable methodological choices on the carbon footprint of different foods. The choices were then discussed in relation to taxation of food. The methodological choices included in the sensitivity analyses were different approaches to system boundaries, how to account for soil carbon changes and how to weigh greenhouse gases (GHGs). Results and discussion The results on the carbon footprint of food calculated with the suggested method are in line with earlier findings in the field, with animal products, especially beef, showing a substantially higher value than most plant-based foods. Regarding choice of system boundaries for using the values in a tax, it is of particular importance to target emissions from biological processes, as these are currently untaxed. This would also be administratively simpler but less acceptable as large emission sources especially for imported products and greenhouse grown vegetables would not be included. Modelling emissions from soil carbon changes using a site-dependent method can be an advantage to obtain results in line with empirical data. Using Global Warming Potential over 100 years to weigh GHGs would be most in line with current climate reporting, which is an advantage for the consistency and acceptability of a tax. Conclusions Ultimately, how taxes are set is a political decision, but food carbon footprint values determined with a consistent and simplified methodology are required in the process. This study presents carbon footprint values established using such method and provides valuable insights into how methodological choices affect the results of climate impact values and the implications for taxation.