An amazon erc number is a unique identifier that Amazon assigns to each seller. It is used to track sales and shipments, as well as to identify the seller when filing taxes. This number is required for sellers who want to use Amazon's services, such as Fulfillment by Amazon and Seller Central. Having an ERC number helps sellers keep track of their transactions with Amazon, which can be useful for tax purposes. Additionally, it helps ensure that all sales are properly reported and that sellers are not missing out on any potential tax deductions or credits.