Welcome to the Q&A Forum

Thank you to both for replies. Gianluca that was exactly the answer I was looking for I guess which showed that I was on the right lines with my own thinking and learning but I also think I wasn't confident enough to assert that to someone developing an ecommerce site themselves from within their own limited resources.

But my initial spot of duplicate content on their site was right, their view is to fix it with robots.txt and no index tags so your excellent second link, Gianluca, and JoelHit's response has enabled me to give them to explain their situation and confidently recommend a solution appropriate to their needs.

Many thanks

First off, SEO learner, not a professional, therefore question is not for any client.

A new (less 1 yr) ecommerce site in a particular sector is now moving into partnership with relevant websites to be their online store. A 'store' link on the partner site will redirect to the ecommerce domain to a dedicated area (on a domain/directory path) with the partner's branding. To do this though means duplicating the entire catalogue for each partner that comes on board for this scheme.

So the original ecommercesite.com/categories also delivers

ecommercesite.com/partner1/categories (with partner's brand identity)

ecommercesite.com/partner2/categories (with partner's brand identity) and so on

Won't duplicating the product catalogue in directories cause problems in delivering effective SERPs for the original ecommerce site?