A binding tariff ruling (known as a Binding Tariff Information or BTI ruling in the EU and UK, and an administrative ruling under CBP in the US) is a formal determination from customs authorities on exactly which HS code a specific product falls under, legally binding on that authority for a set period, typically three years in most jurisdictions.
Requesting one makes most sense for a product whose classification is genuinely ambiguous — a multi-function item that could reasonably fall under more than one heading, or a new product category without an obvious precedent — rather than for routine, well-established goods where the correct code is not in real doubt.
The process requires a detailed product description, often technical specifications or samples, and takes weeks to months depending on the authority and product complexity, so it is a pre-shipment planning step for a new, ambiguous product line, not something requested once cargo is already moving.
The benefit is removing classification risk from a specific product permanently — rather than making a reasonable classification judgment and hoping it holds up to a later post-clearance audit, a binding ruling settles the question in advance and shifts the burden of any later dispute onto the ruling itself rather than the importer's original judgment call.