The process to update the UPC to GS1 barcode involves creating a duplicate listing that is exactly the same as the one you need to update the UPC for. After creating a duplicate copy of your original listing, you will need to merge them to attach the GS1 barcode to your listing.

IMPORTANT BEFORE PROCEEDING: Go to Inventory Reports and download a Category Listings Report (CLR). Keep it until the task is complete. This file will serve as your backup in case of data compromise.
1. The first step is to check the ASIN's backend to see if a UPC is attached to it. Make sure to check the upper part.
See the Screenshot below:

If you can see that there’s no UPC attached to it (Upper part), you can simply upload a flat file to update the UPC on the SKU.
If there’s UPC attached then proceed with the next steps below:
Method 1: DIRECT EDIT ON BACKEND
Create a new ASIN with the correct UPC barcode (which is bought from GS1):
- One way to do this is by copying the listing on Manage Inventory and entering the new UPC code.
Go to the original listing, click on edit, and Copy Listing

Create a new SKU. You can add “-1” to the SKU.
For example, The original listing has the SKU: ABC
You can put ABC-1 then put the correct UPC and upload the image and then click Save and finish
NOTE: You may need to fill in some other information, just copy the information from the original listing. Please see the sample images below for reference.


Method 2: FEED (FLAT) FILE UPLOAD
Another way to create a new ASIN is by uploading a feed file using the CLR. To create a new ASIN, you need to filter out the problematic SKU from the CLR, create a copy of it by altering the SKU, and place the correct barcode.
Use a feed file to copy the original listing. You can add “-1” or “-duplicate” on the SKU and place the correct UPC.
Please see the sample images below for reference.

NOTE: Remove the original listing and any other listings from the flat file, and only keep the duplicate listing, then perform a partial update. This is to ensure that we avoid any data mix-up.

Once the duplicate has been created, it will generate a new ASIN, and you may proceed with creating a case. Make sure that the duplicate listing is not suppressed; otherwise, Amazon will not proceed with the process.
After doing either of the methods above, create a ticket with seller support. Provide the original and recently created ASIN and the correct UPC barcode in the ticket:
USE THIS TEMPLATE:
In short description: SAS Support | UPC Change

Please escalate this to the leadership team.
Our listing was created with a random UPC code instead of the proper GS1 registered barcode. We were told by one of your colleagues that we have to create a new listing, merge it with our original ASIN and then cleave out the incorrect UPC.
Attribute to Update - UPC code
– Original ASIN
ENTER_ASIN
– Correct Product Identifier
ENTER_GS1_BARCODE
– New ASIN
ENTER_RECENTLY_CREATED_ASIN
– Incorrect Product Identifier
ENTER_CURRENT_PRODUCT_ID
Here is the path forward to fix this issue:
(Correct Product Identifier) is now assigned to ASIN (New ASIN)
We need to merge the ASINs first and the target should be (Original ASIN)
Then cleave the offers with incorrect UPC (Incorrect Product Identifier).
NOTE: Make sure to keep the ASIN (Original ASIN)
If the case has been responded to and Amazon has made the changes, check the back end of the listing and see if the correct UPC is displayed on the product information. If it is not:
- Upload a partial update feed file with SKU, product id type, and product id (GS1 Barcode).
- If the UPC code does not get reflected on the backend, reopen the case.
Reminder: This task requires lots of back and forth with the seller support and 85-90% of the time, they reject your requests. I suggest being persistent and keep creating cases until it is resolved. Most of the representatives in the seller support team are not aware of a solution to fix this issue or they are not willing to help.
Common Issues that Amazon might do in the listing while in the process of UPC change.
Amazon might create a new ASIN under the original SKU and the original listing will be in the fixed stranded Inventory

Search the suppressed SKU in fix stranded list

A. To fix this, delete the search-suppressed ASIN (The ASIN that Amazon has created)

It may take up to 5- 15 minutes to take effect.
Make sure that it is deleted, you can search the SKU to double-check if it is no longer in the managed inventory.
The next step is to relist the original listing, you can relist it from the fix stranded Inventory page or add it manually
Proceed to B if we don't have access to fix the Stranded Page
- To Fix in fix stranded Inventory just look for the original ASIN and click on Create New Listing

It will redirect you to a page to recreate the listing and just fill in the price and click save and finish.
It may take up to 5- 15 minutes to take effect and see the original listing back in inventory.
How do we know if it’s fixed: The listing should disappear from stranded inventory and ASIN should show as “Active” in your inventory.
B. Add it manually, Copy the original ASIN, and go to Catalog>Add Products

Paste the ASIN in Find your products in Amazon's catalog and press the search icon

You will be redirected to this page just click on the Select condition to NEW and then click on Sell this product button

Fill in the original SKU and the price and Click Save and Finish

NOTE: It may take up to 5- 10 minutes for the original listing to show up on the manage Inventory page.