There is a huge difference between standards. Some standards are intention based and some are inspected. Some covers only a few tiers of suppliers and a few the entire supply chain.
GOTS is based in Germany and is often referred as the most strict standard in the entire textile industry.
In GOTS all suppliers in the supply chain, including packaging and trims, have to be certified themselves in order to be a part of a GOTS supply chain. The supply chain starts at the farmer, continues to the mill, dyeing house and loom factory to the sewing house and the brand holder.
All entities are inspected once a year and all up to brand holder have unannounced inspections. And the certifiers are only to be appointed by GOTS.
In order to be sure of the sold quanity not exceeding the harvested amount, all of us in the GOTS supply chain have to document the amount bought and sold. This is done by TCs. TC means Transaction Certificate. And can only be issued by a certified based on a lot of info such as shipping paper, purchase documents etc.