Field help (GTEGRPCOD) 

This field is only active for DetailVAT box types. It is not mandatory.

The entry type group code legislation must be consistent with the legislation entered in the Company legislation field. It must either be empty or identical.

This field works together with the Entry type field and are mutually exclusive.

This setup allows you to enter one combination rule line instead of multiple lines due to different entry types to consider for the same Tax management + Tax allocation + Tax code setup line.