Parcel data supports planning, assessment, environmental management, and emergency response, among others. Differences in how this information is created and maintained, and the lack of shared guidelines, limit its usability statewide. Municipalities are required by law to submit GIS parcel and assessor data to their Councils of Governments, who voluntarily share it with the CT GIS Office for statewide aggregation. While compiling data from 169 municipalities, significant variations in quality and consistency have been identified. In response, the GIS Advisory Council’s Parcel Data Creation Working Group and the GIS Office developed the Connecticut GIS Parcel Data Creation Guidance and Specifications. Drawing on expert knowledge, this guidance offers a practical framework and best practices to improve consistency, accuracy, and interoperability. This presentation reviews the statewide needs that led to its development, the recommendations, and their value for better decision making.