Audit in the EU is not only ruled by law but also by audit standards which stem from the international audit practice. What are the implications of general principles of EU law for audit practice? This paper sets out to provide some insights into those principles of law as they are relevant to auditors. For example, in cases concerning access to information or retroactive application of rules, the principles of proportionality and legal certainty are highly relevant both for auditors and for beneficiaries of EU funds. For that reason auditors should apply general principles of EU law during the audit process and use them as a frame of reference in applying audit standards. Principles of good audit need to encompass a number of these general principles of EU law. For beneficiaries of EU subsidies, the application of these general principles of EU law in audits is fundamental so that they may perceive that they are being treated fairly and in order to develop a relation of trust between auditor and auditee.