How to well structure a product sheet
Prerequisite
Only one major point; The SKU has and must be unique for the entire catalog.
Product
To be exported to Amazon efficiently, without hassle, an ideal product sheet should be structured like this;

Having comprehensive product information and classification
Vendor, by default, will be exported as Brand to Amazon
Product type is helpful to classify, search, include or exclude products
The App is collections-based, the best is to classify its products by universe and accurate product type
Having products tags helps for search, classification, refinements

Variants
The SKU has and must be unique for the entire catalog even for variants.

It is imperative that the SKU be unique. It is paired with the barcode: one unique SKU/barcode pair per product or product variant.
Note that the same barcode cannot be assigned to more than one product or variant.
The SKU is the sole identifier that helps to identify the product on Amazon.
Barcodes
Barcodes (GTIN, UPC, EAN...) must be officially issued by GS1.
By adopting barcoding for your product catalog, you substantially increase the trading power of your products. This will become a core factor influencing your development in the marketplace.
So, we see that product labeling with an official barcode eases penetration of distribution networks, such as the supermarkets and hypermarkets and, of course, the global marketplace overall.
Therefore, acceptance of the barcode standard will clearly increase your business, making the necessary outlay, in the form of an annual subscription payment to GS1, a marginal issue in comparison to the added value your catalog will acquire.
EAN bar-coding also significantly affects the referencing of your product: Inclusion of the EAN barcode in search engine queries ensures the listing of your site in the search results.
Magic barcode websites or generators
Yes, definitely, GS1 barcodes are expensive, everybody wants to find a cheaper alternative.
You will find thousands of websites, barcodes generators, etc. Some are even issuing certificates, certificates of authenticity, the only authenticity of those barcodes is that you have been taken for a fool.
All those solutions are not legal. GTINs are the property of the GS1 company.
Amazon informs well about barcodes usage;

Unicity and common mistakes
A barcode is unique. It can be associated to only 1 product. It can't be split, shared, the most common mistake is thinking that a pack or a set of products has the same barcode as the sole product itself;
Wrong usage sample;

Any doubt? Go to your supermarket, take one pack of bottles and look at the pack barcode and the barcode on each product that is in the pack; the product itself has a different barcode than the pack.
Barcodes exemption
Barcoding is generally required for all manufactured products, but not for cottage industry or crafted jewelry products (...).
However, in some cases, determined by the preferences of the target marketplace, the manufacturers or their exclusive distributors may obtain an exemption from the barcoding requirement for their products.
For some categories, the situation is even simpler: there is no need for any EAN barcode at all. This ruling is universally applied in all marketplaces.
In all cases, it is necessary to inquire Amazon to create products without barcodes;
Americas; https://sellercentral.amazon.com/gtinx Europe; https://sellercentral.amazon.co.uk/gtinx Far East; https://sellercentral.amazon.com.au/gtinx
Updated on: 14/01/2025
Thank you!