Exchange of Notes

An exchange of notes (also called an exchange of letters) is a treaty in simplified form, concluded when one state sends a diplomatic note proposing the terms of an agreement and the other replies with a note accepting or confirming those terms in identical or matching language. Together, the two notes constitute a binding international agreement.

The practice is recognized under the Vienna Convention on the Law of Treaties (1969), Article 2(1)(a), which defines a treaty as an international agreement "whether embodied in a single instrument or in two or more related instruments and whatever its particular designation." Exchanges of notes are therefore treaties in the legal sense and bind the parties under international law, even though they avoid the more formal procedures of negotiation, signature, and ratification associated with conventions or treaties styled as such.

Governments typically resort to this instrument for matters that are:

• technical or routine (e.g., visa arrangements, air services, taxation, customs cooperation);
• implementing or amending an existing framework treaty;
• time-sensitive, where speed is preferable to a full treaty negotiation.

Notes are usually exchanged between a foreign ministry and a resident diplomatic mission, or between two foreign ministries directly. The reply note quotes the proposing note in full before stating acceptance, ensuring textual identity. Entry into force is commonly the date of the reply note, unless the texts specify otherwise.

Despite their informal appearance, exchanges of notes carry the same legal weight as more elaborate treaties and are typically registered with the UN Secretariat under Article 102 of the UN Charter. Domestically, however, they often do not require parliamentary approval, which makes them politically attractive for executive branches seeking flexibility. Critics argue this can bypass legislative oversight on substantive matters, blurring the line between executive agreement and treaty.