Service of documents: cross-border tax documents must be served by domestic methods or requested equivalents with translation safeguards. Service of tax-related documents must be made by the requested State using methods prescribed by its domestic law or, where possible, by a method requested by the applicant State or the closest available equivalent; direct postal service between Parties is permitted and service in accordance with this article is not invalidated by a Party's domestic law. Documents served need not be translated unless the addressee cannot understand the language, in which case the requested State must arrange a translation or summary or may request the applicant State to provide one in an accepted official language.