Policies for supporting biofuels, such as the EU’s Renewable Energy Directive RED, the Renewable Fuel Standard in the US, and the UK’s Renewable Transport Fuel Obligation (RTFO), require life cycle carbon reporting to ensure that biofuels achieve greenhouse gas reductions relative to fossil fuels. These policies tend not to distinguish between two types of life cycle analysis (LCA); consequential LCA (CLCA) and attributional LCA (ALCA). Failure to distinguish between CLCA and ALCA can result in the wrong method being applied, a combination of the two approaches within a single analysis, a misinterpretation of the results, or an unfair comparison of results derived from different methods. This paper sets out the key differences between CLCA and ALCA and assesses which method is applied in the carbon reporting guidance for the RTFO and RED, or whether a mixture of the methods is used. We find that the RTFO guidance adopts a partial CLCA approach but that there are inconsistencies in the treatment of co-products and ALCA derived fossil fuel comparators are compared to partial-CLCA biofuel values. The LCA method used in the RED is largely consistent with ALCA, but this may not be the most suitable method for determining total greenhouse gas impacts, which is one of the main purposes of carbon reporting in relation to biofuels policy.