Country
Packaging rules in Spain
The EU-wide rules apply in Spain the same way they apply everywhere else — those are on the rules page. This page carries its producer register and the ministry to start with.
Where businesses register
Spain keeps its list of packaging businesses in Registro de Productores de Producto, packaging section, run by the Ministry for the Ecological Transition (MITECO). The rules call this a producer register, and being on it is what allows packaging to be made available there at all, so it is usually the first thing a business shipping there deals with.
Source: Registro de Productores de Producto, packaging section, run by the Ministry for the Ecological Transition (MITECO) — read from this source on