There is no rule about them being horizontal or vertical, but there is one about curved surfaces. Is it possible that it was placed horizontally along a curved surface whereas if it was vertical it would be more easily scannable?

Thanks Demel.

I have seen many bottled products with a horizontal barcode, maybe he was just one of the unlucky ones.

It will cost me time and money to get my barcode altered, how would you advise me to proceed? The FNSKU I understand, if it’s going over an edge it can cause a crease in the barcode, making it unscannable etc. However would this be the case for GTIN barcode which is actually part of the label ?

Just to to respond to your post, it isn’t really about creases in labels or barcodes. It’s about the scanner being able to see the whole thing without someone having to manipulate the product to try and get the whole barcode visible.

GS1 have a guide on barcodes which has way more info than anyone should ever need, but they do talk about horizontal vs vertical and circumferences on page 7:

It all does though come back to what Amazon actually told your friend about their barcode placement. It’s possible all of this is a red herring and Amazon either meant something else or made a mistake.