The short answer
Whether you need a declaration of conformity for your shipping box depends on who places the packaging on the market and what type of packaging it is exactly. The European Packaging Regulation requires anyone who places packaging on the market to be able to demonstrate that those packages meet the requirements, and this is done with a declaration of conformity and an underlying technical file as described in Annex VIII of the Regulation. A shipping box that you yourself purchase and use to package orders falls under this in most cases, even if the box itself bears no brand or logo.
The point where things often go wrong is the assumption that only product packaging — the box or bottle in which the product itself is sold — counts and that the cardboard outer box that serves only to send something gets exempted. That distinction does exist in the Regulation, but it does not align with what people intuitively think. Shipping packaging is a separate category with its own requirements, not a category that is exempt.
Product packaging and shipping packaging are not synonyms
The Regulation distinguishes between different packaging levels: packaging that directly surrounds the product, packaging that bundles products, and packaging that serves to transport or ship. An online shop that sells clothing loose in a plastic bag and then places that bag in a cardboard box for shipment is dealing with two packaging layers that can both fall under the Regulation. Both layers can potentially require their own declaration of conformity, with the understanding that the nature of the obligation may differ per layer.
This is precisely the detail this topic hinges on: whoever assumes that only the product itself and the direct packaging around it is relevant often leaves the shipping box unaddressed in their own file. However, supervisory authorities and certifying parties look at the complete packaging chain that a company uses, not just the part that the customer sees first.
When this applies to your situation
Whether and how this plays out for a specific business depends on who in the chain qualifies as the manufacturer of the packaging, in which country the packaging is placed on the market, and whether there is own branding on the box. That is precisely why a general explanation cannot go further here than outlining the distinction: the role you perform — manufacturer, importer, or something else — determines whether the obligation rests with you or with a party further down the chain. Whoever wants to check this per packaging type can run through it in a few questions and get an immediate indication without needing an account for it.
What belongs in a declaration of conformity and file
A declaration of conformity is not a standalone form but a summary of an underlying technical file. That file typically contains data on the materials used, the way the packaging is reusable or recyclable, and a substantiation that there are no unlawful quantities of heavy metals or certain substances such as PFAS in the packaging. In addition, the name and address of the responsible party must appear on the packaging or in the accompanying documentation. For a shipping box, this means in practice that it is not enough to know who supplies the box; there must also be evidence of why that box meets the material and design requirements.
Drawing up and maintaining such a file is a recurring task, especially when a company changes suppliers or adapts the design of the shipping box. Those who prefer not to work out themselves which template and which substantiation applies to each packaging type can have that part set up within the packaging file of the subscription instead of reconstructing this for each shipment anew.
What you can already check yourself
Without immediately building a file, it is useful to check the shipping box you use to determine what material it is made of, whether it bears your own brand, and whether the same box is also used in other countries. These three pieces of information largely determine whether the obligation lies with you as the sender or with the supplier of the box. More background on how this classification is structured in the regulation is neatly compiled in the knowledge base by topic, and anyone wanting to know where that information comes from can find that in the explanation of the sources used.
If after reading you still have doubts about whether the shipping box you use falls under your own responsibility, then a legal assessment in borderline cases is something for which the guidelines of the European Commission or a lawyer remain the appropriate point of contact. For an initial, free indication of your situation, the role finder is a logical starting point, and anyone who prefers to browse the broader topics right away will find them compiled in the knowledge base.