There are two companies, A and B. Company A holds the TUV master certificate and Company A produces a certain product. Company B wants to let Company A do OEM work and sell the products of Company A, but it must be authorized by Company A, so Company B needs to hold the secondary certificate of Company A's main certificate. For example, company A's TUV certificate was obtained in TUV Rheinland, so company B needs to pay a certain fee to handle company A's secondary certificate.

Hehe, I am in charge of TUV sub-certification and UL listing for many times in our company. This is my experience, I hope I can help you. If you still don't understand, please leave me a message!