Article 21 outlines the framework for administrative cooperation among GCC Member States regarding excise tax. Following a proposal from the GCC Secretary General to the Ministerial Committee, states can implement cooperative measures in specific areas. These include exchanging information upon request to determine tax accuracy, agreeing to simultaneous auditing procedures, and participating in audits conducted by another Member State with its approval. The article also mandates assistance in the collection of tax. A crucial provision obligates Member State employees to maintain the confidentiality of information received from other states, restricting its use to official duties, with each state permitted to set penalties for violations.