Model, batch or item: what should a product tag identify?
The act for the product group decides: Article 9 lists the level among the things it specifies, and Article 10 requires the passport data to refer to it. Below the law, the level sets the cost of encoding, the chip you have to buy and what a tap can do after the sale.
The level comes from the act
regulation (EU) 2024/1781 puts the question in the delegated act. Article 9 lists, among the things the act specifies, whether the passport is to be established at model, batch or item level, and the definition of such levels; Article 10 requires the data included in the passport to refer to the level the act set.
So the first answer is not a design preference. Read the act for the group, and treat what follows as the engineering that flows from its choice.
What each level costs to encode
A model level identifier is the same string on every unit, which means one message written once and copied, and no record tying a tag to a unit. It is the cheapest thing a production line can do, and the bulk writing page covers how that scales.
An item level identifier is a different string on every unit. Either the line writes each tag individually, which is a per unit operation with a record to keep, or the chip contributes its own identifier: a chip that mirrors its factory identifier into the content lets a thousand identical writes still arrive distinguishable, which the unique URL page explains and the server side page takes from the receiving end.
Batch level sits between the two, with one write per batch and a record that says which batch a unit belongs to, which is usually the line's existing lot record rather than a new one.
The chip decides more than the price
Mirroring cannot be added later. A chip without it forces individual encoding for item level, and that decision is made when the tags are bought rather than when the passport is designed, which the chip choice page makes for the general case.
The same goes for memory: an item level address is longer than a model one, and a batch qualifier longer still. Checking the longest address the scheme can produce against the tag memory belongs to the specification, not to the first production run.
What the level buys later
Model level answers what a product is. Item level answers which one this is, and that difference is what makes a warranty, a repair record, a recall or a transfer of ownership attachable to the object in a hand rather than to a catalogue entry.
It also carries a privacy question, since an identifier unique to one object can follow the person who owns it, which the data protection page frames and which the passport itself keeps out of scope by excluding customer data without consent, as the access page describes.
Frequently asked questions
Who decides the level?
The delegated act for the product group. It specifies whether the passport is established at model, batch or item level, and defines those levels.
Is item level much more expensive?
It is a different operation: individual writes and a record, unless the chip mirrors its own identifier, which lets identical writes stay distinguishable.
Can I change the level later?
Not for tags already made. The chip and the address length are chosen at purchase, so the level is settled before the order.
Does item level identify a person?
Not by itself. It identifies an object, and the passport excludes customer data without consent, but a per item identifier can follow an owner, which deserves a decision.