Letter the Commission sends to a Member State, in particular in application of Article 86 of the EC Treaty, when it is alleged that the Member State enacts or maintains in force a measure which is contrary to EU competition rules. A letter of formal notice is the procedural equivalent to a statement of objections sent to undertakings.

Source: Glossary of terms used in EU competition policy, Antitrust and control of concentrations, European Commission, 2002