EU legislation must be flexible enough to be relevant and workable across all Member States. Accordingly, the legislation is not always very prescriptive and implementation can be complex and challenging for authorities and stakeholders. To address these issues, the EU frequently adopts guidance documents such as formal official communications or notices, practical handbooks building on advice and proven approaches from different Member States, and interactive online tools. Preparing guidance documents requires in-depth understanding of the legislation, practical familiarity with different implementation approaches across the EU, and significant research into good practices, success factors, and lessons learned. EU-wide guidance must be sufficiently broad to be relevant across different Member States’ contexts, but specific enough to be of actual use to the target audience. Milieu supports the European institutions to prepare guidance documents that can underpin proper and better implementation of EU legislation.