ArchiCAD setup

From Wiki.OSArch

IFC GlobalId[edit]

The IFC GlobalId generated for the IfcProject, IfcSite, IfcBuilding, and IfcBuildingStorey depends on the values you put in the File > Info Project Info dialog box. This means that it is important to fill out these values correctly with project specific information. If these are left blank, or have data from a different project, it will run the risk of generating a GlobalId which is not unique to the project.

Read more at How to Control Global ID (IFC Attribute) Based on ARCHICAD Project Info.