This user guide accompanies the Excel-based Immunization Data Triangulation Tool (IDTT) that triangulates immunization services statistics with supply chain data to produces key indicators and performance scores and provides recommended actions. The guide provides instruction on how to use IDTT, as well as information on for conducting the data triangulation process and how to use the process for decision-making. It is divided into four key parts: 1) Why triangulate data, 2) IDTT step-by-step instructions, 3) Understanding the results, and 4) Data review and decision-making.