This guide provides guidance for writing advocacy briefs for the harmonization of resource tracking methodologies for the System of National Health Accounts (SNHA) and AIDS Spending Assessment (NASA). It describes the key steps: defining the target audience, understanding their point of view to adapt the message, and disseminating the note via preferred channels. The document recommends adapting language to the audience’s technical level, being concise, using illustrations and presenting reliable evidence. It presents practical solutions to common challenges: reducing costs and duplicate collections through consolidated questionnaires, combining collection and purification steps to limit duplication, and ensuring that skilled teams are available who master both CNS and NASA methods. To ensure the availability of detailed data on HIV-related expenditure, it recommends the integration of NASA coding elements into consolidated tools, and appropriate disaggregation. The text sometimes advises conducting separate analyses after common collection to avoid CNS data volumes delaying the release of NASA results, while warning of the risk of discrepancies between totals if data sets are modified. Finally, it stresses the importance of adapting recommendations to the national context and the priorities of stakeholders. The guide was made possible thanks to support from USAID, and is the responsibility of Results for Development and its partners, including those explicitly mentioned above.