The recommendation requires unannounced audits for all legal manufacturers who certify under one of the European Medical Device Directives (AIMDD, MDD, and IVDD). ... An unannounced audit can be nerve-wracking for even the most buttoned-up organizations, but there's a lot you can do to prepare yourself and your staff.

Why should audits be unannounced?

Unannounced audits are designed to ensure that a product is being manufactured in compliance with the quality management system. Companies selected for audit must provide full access to their manufacturing processes, as well as quality, batch, and purchasing records.

Should audits be announced?

If it's a management system (ISO 9001) type audit, then yes, it should be announced. There is NO good reason to treat people as if they have been caught with "their hand in the cookie jar".