We purchased an existing business. There are currently several sellers of our product on Amazon, which has three sizes and three separate ASINs and UPC codes, some we sell to and others must be getting our product from a distributor. It seems the original owner of the business purchased the three UPC codes from a broker many years ago. When I look up in GS1, it is that business that the codes are registered to. That business is now closed. I registered with GS1 and now have 3 new UPC codes with our own company prefix. I have the brand registered in brand registry, but that's all I have done there. I have set up a seller account. I have not sent Amazon any product yet.

I don't yet have the product packaging with the new UPC codes and that will take weeks to months since we have solid inventory of the packaging with the original UPC codes to use up first. Should I just start selling on Amazon using the existing ASINS/product listings that others have created for now and then create new listings linked to the brand registry when we have the packaging with the new UPC codes?

Regardless of which UPC codes are being used to sell on Amazon, will I always be covering them up with a FNSKU? Or does that depend on other factors?

We also sell wholesale to various shops. Hopefully I provided enough info to get some answers on this. I have zero selling experience on Amazon and don't want to make any more mistakes than I already have. :) Thanks in advance for any answers and advice. The more articles I read and videos I watch, the more confused I get. :(