First verified institutional greenhouse gas inventory of a Costa Rican municipality, covering fiscal years 2020–2025. Total emissions: 164,172.53 tCO2e across six source categories. Aligned with IPSASB SRS 1 (Climate-related Disclosures, effective January 2028), adopted in advance. Dominant source: Relleno Sanitario Los Llanos landfill (80.81%, Scope 3, IPCC 2006 First Order Decay method). Supporting dataset for research article submitted to Public Money & Management on GHG inventory recognition under IPSAS 19. Public dashboard: https://akademoslab.com/apps/srs1-msc/