What happens if I upload a flat file with duplicate SKUs to Amazon Seller Central?

Amazon processes each row sequentially. Duplicate SKUs in the same feed can result in conflicting updates, suppressed listings, or feed processing errors depending on the template type. Removing duplicates before upload prevents these issues.

Should I deduplicate on 'seller-sku' or 'asin'?

For inventory update feeds, deduplicate on 'seller-sku' since that is your unique identifier in Seller Central. For research or catalog files where you're working from ASIN lists, deduplicate on 'asin'. Use whichever column represents the unique entity you're managing.

Will this preserve Amazon's required flat file column structure?

Yes. Deliteful preserves all columns and their order exactly as they appear in the input file. Amazon flat file templates have strict column requirements and the output will match the input structure.

Can I use this for FBA shipment CSVs as well as listing flat files?

Yes. Any CSV with a column that should contain unique values can be deduplicated with this tool. FBA shipment files, inventory feeds, price update files, and listing templates are all supported.

Remove Duplicate ASINs and SKUs From Amazon Flat Files Before Upload

Amazon flat files and inventory CSVs built from multiple supplier sheets or catalog exports frequently contain duplicate ASIN or SKU rows — and uploading a flat file with duplicate entries to Seller Central causes suppressed listings, conflicting price updates, and feed processing errors. Deliteful's CSV Deduplicate tool strips those duplicates before the file ever reaches Amazon.

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Sellers managing catalogs of hundreds or thousands of SKUs often assemble flat files by combining exports from multiple suppliers, repricing tools, or inventory management systems. When the same ASIN appears twice in an inventory update feed — with different prices or quantities — Amazon processes both rows and the result is unpredictable: the last row may win, the listing may be suppressed, or the feed may error out entirely. A duplicate SKU in a new listing upload can trigger a 'SKU already exists' error that blocks the entire batch.

Deliteful resolves this before upload. Specify 'seller-sku' or 'asin' as the key column, upload the assembled flat file, and download a clean version with only the first occurrence of each identifier retained. The original column structure — which Amazon's flat file templates require exactly — is preserved. The output is ready to upload directly to Seller Central's Add Products via Upload or Inventory File Upload workflow.

How it works

1
Assemble your flat file or inventory CSV
Combine your supplier exports, repricing tool output, or catalog data into a single CSV.
2
Upload to Deliteful
Drag the assembled file into the CSV Deduplicate uploader.
3
Enter your key column
Type 'seller-sku' or 'asin' — whichever column should be unique in the file.
4
Download and upload to Seller Central
Get the deduplicated flat file and upload it to Amazon via Add Products via Upload or Manage Inventory.

Frequently asked questions

What happens if I upload a flat file with duplicate SKUs to Amazon Seller Central?: Amazon processes each row sequentially. Duplicate SKUs in the same feed can result in conflicting updates, suppressed listings, or feed processing errors depending on the template type. Removing duplicates before upload prevents these issues.
Should I deduplicate on 'seller-sku' or 'asin'?: For inventory update feeds, deduplicate on 'seller-sku' since that is your unique identifier in Seller Central. For research or catalog files where you're working from ASIN lists, deduplicate on 'asin'. Use whichever column represents the unique entity you're managing.
Will this preserve Amazon's required flat file column structure?: Yes. Deliteful preserves all columns and their order exactly as they appear in the input file. Amazon flat file templates have strict column requirements and the output will match the input structure.
Can I use this for FBA shipment CSVs as well as listing flat files?: Yes. Any CSV with a column that should contain unique values can be deduplicated with this tool. FBA shipment files, inventory feeds, price update files, and listing templates are all supported.

Create your free Deliteful account with Google and clean your Amazon flat files before your next Seller Central upload.