The document does not have major issues, so it can be considered "ready". However the way the document is written is often very narrative, instead of preferring schemas, diagrams etc. and this can sometimes confuse the implementer while reading it. Here are my suggestions for improvement: - the abstract can be shortened just to specify directly why we need this extension - there are in section 3 cases where the sentence id a double negative (a MUST NOT followed by a negative sentence). They are correct, but may I suggest to turn them into a single positive (a MUST and a positive sentence to follow) ? - a "query", "response" etc flow schema may help in making sections 3 less narrative and more easy to read - all examples are just "US centric" (e.g. using US style postal addresses): I would suggest considering also examples take from other different postal addresses schema, both to show how they fit into the schema itself - there are some typos/nits to fix with a proof reading all the best