The short answer
The CSRD (Corporate Sustainability Reporting Directive) is a European directive that requires certain enterprises to report on sustainability in their annual report: environmental impact, social aspects and governance. For most SMEs, the directive does not apply directly. The criteria concern the size of an enterprise, measured by, among other things, the number of employees, turnover and total assets. Which thresholds exactly apply and for which companies is set out in the directive itself and the national legislation based on it.
Yet many smaller suppliers do notice something of the CSRD, and that is usually the reason you are reading this article. A large customer who is themselves covered by the directive must also say something about their supply chain in their own reporting. To gather that information, they send a questionnaire to their suppliers. You are then not reporting yourself under the CSRD, but you are supplying data to someone who has to do so.
What the directive itself regulates
The CSRD requires designated enterprises to report according to a fixed standard, the ESRS (European Sustainability Reporting Standards). This includes topics such as energy consumption, emissions, working conditions in the supply chain and governance structure. The directive does not require every sub-supplier to report themselves; it requires the reporting enterprise to provide a complete picture, and part of that picture is with its suppliers.
Whether an enterprise is covered by the directive, and from when, may differ per country and per business type in the implementation. For the exact thresholds and the date from which an enterprise must comply, the official text of the directive and its implementation in your own country is the proper source, not a summary on the internet.
Why you receive a questionnaire without being subject to reporting requirements yourself
A large customer who is covered by the CSRD must demonstrate what happens in their supply chain in terms of sustainability. Because they cannot measure all of this themselves, they ask their suppliers. This explains why, for example, an installation company with twenty employees sometimes receives an extensive sustainability questionnaire: not because the company itself is subject to reporting requirements, but because it is part of the supply chain of a customer that is.
For smaller enterprises, there is a simplified, voluntary standard for answering this type of question. What that standard looks like and which documents belong to it is explained in the article on the VSME sustainability questionnaire. The difference between that voluntary standard and full CSRD reporting is precisely the difference between supplying data and reporting yourself.
Directly affected or only as a supplier
It is not always immediately clear to an entrepreneur on which side they stand. A company may fall well below the thresholds in one year and the next year, through growth or through an acquisition, suddenly approach the limit. A change in group structure, for example because a company becomes part of a larger group, can also affect the question of whether the directive applies directly.
Whether your enterprise is itself covered by the CSRD is a question that a lawyer or accountant with knowledge of the current thresholds can answer on the basis of your annual figures and structure. This article describes the distinction, but does not provide an opinion on an individual situation.
What you can do practically with it
For most readers of this article, the question is not "do I fall under the CSRD", but "why is my customer asking this" and "what should I do with this". The answer to that second question is usually: collect the requested data, keep it in order for the next year, and submit it in the format that your customer uses. That format differs per customer, even though the content often covers the same topics.
Because each customer uses their own portal and their own questionnaire, it is useful to keep your answers in one place and fill them in repeatedly from there, rather than treating each questionnaire as a new project. This keeps the approach manageable, even if the number of questionnaires increases.
Check whether this applies to you
If you are not sure whether a questionnaire from your customer has anything to do with the CSRD, NIS2 or another European obligation, that in itself is already a useful signal to investigate the subject further. In the knowledge bank with explanations by topic you will find a brief explanation for each term, with the source in the official text.
If you first want to get an impression of which obligations may be relevant for your company, you can see in a few questions where you approximately stand. That does not provide a legal opinion, but does give you a first direction. For questions about how the information on supplia.eu comes about, read more on the page about where the information comes from.
If you have a concrete question about your own situation after reading, look at the answers to frequently asked questions or submit the question to a lawyer or accountant. If you want to get started right away with the questionnaire on your desk, you can do the free quick-scan without obligation to see which topics seem applicable to your company.