Sustainable Development Goal (SDG) financing is gaining global interest in the Decade of Action (2020–2030). Without an adequate assessment of the SDG financing flows, government actions can fail to accelerate SDG achievement. This document presents an SDG budget-tagging methodology to measure and strengthen countries’ SDG financing diagnostics. The methodology can be applied to (i) national and subnational budgets; (ii) international development cooperation to strengthen its monitoring; and (iii) identifying potentially eligible projects in private financing strategies. In addition to strengthening SDG financing diagnostics, when accompanied by data visualization tools, SDG budget tagging can strengthen fiscal transparency by communicating government action to the public using the 17 SDGs and inform SDG-oriented budgetary policymaking.