# Technical Support

- [Product IDs](/technical-support/product-ids.md): Amazon uses multiple product IDs - ASIN, SKU, FNSKU, UPC, EAN and GTIN
- [GTIN / UPC / EAN Exemption](/technical-support/product-ids/gtin-upc-ean-exemption.md)
- [Brand Protection](/technical-support/brand-protection.md)
- [Sign up for Brand Registry](/technical-support/brand-protection/sign-up-for-brand-registry.md)
- [Add another account or market to Brand Registry](/technical-support/brand-protection/add-another-account-or-market-to-brand-registry.md): How to add a secondary user to Brand Registry to authorise a new account or a second marketplace.
- [Update product listings with Brand Registry Support](/technical-support/brand-protection/update-product-listings-with-brand-registry-support.md): For brand registered sellers: To update a product listing when edits via Seller Central or Flat File does not work.
- [Counterfeit complaints via Brand Registry](/technical-support/brand-protection/counterfeit-complaints-via-brand-registry.md): How to file a counterfeit complaint in Brand Registry
- [Customer Service](/technical-support/untitled-1.md)
- [How to contact a customer](/technical-support/untitled-1/how-to-contact-a-customer.md)
- [Issue a Refund](/technical-support/untitled-1/issue-a-refund.md): How to issue a refund after a return request is authorised and the returned product is accepted
- [Remove Negative Feedback](/technical-support/untitled-1/remove-negative-feedback.md)