In 2 words, almost everything.
The GST law has a major focus on compliance and the entire GST Network is technology driven, making stronger internal processes within companies essential.
Goods are classified under the HSN code system with each HSN code has its own tax rate. Services are defined under HSN Service Code and each service would potentially have a different tax rate based on its HSN Service Code.
These codes need to be mentioned in the monthly returns filing into the GST Network by each registered entity.
It's best to contact a consultant to guide through the operational & statutory differences which need to be made in your business.