A GTIN number that has already been assigned to a product MUST NOT be assigned to another product. 

The only exceptions are:

A GTIN may be deleted from all catalogs without previously being marked as withdrawn or discontinued, and it may be reused 12 months after its deletion or after its last notification to a trading partner (whichever is later) if both of the following conditions apply:

1. The GTIN is published in a way that makes it accessible outside the company (e.g., in a catalog or directly to a trading partner) under a status indicating that the product is a sample, draft, exploratory, or in an equivalent condition other than final, withdrawn, discontinued, or deleted, and
2. The trading partners to whom the GTIN is communicated agree that it may be reused, either as a condition for receiving the data (e.g., the GTIN is sent to trading partners as part of a research product development phase) or after deletion (e.g., all trading partners confirm that the sample, draft, or exploratory GTIN has not been propagated to a system that would be negatively affected by the reuse of the GTIN).

• If the GTIN was never published in a way that made it accessible outside the company (e.g., recorded in a registry or communicated directly to a trading partner), it may be reused immediately.

• Goods that have been withdrawn from the market and reintroduced can use the original GTIN if they are reintroduced without modifications or changes that require a new GTIN, according to the GTIN Management Standard.