Exchange of information procedures clarified, including acknowledgement timelines and defined recoverable extraordinary costs for tax cooperation. The Protocol permits competent authorities to consult the OECD 2002 commentary when interpreting identical exchange of information provisions, requires written acknowledgement of requests and notification of deficiencies within sixty days, mandates prompt explanation if information cannot be obtained or provided within ninety days, and delineates recoverable extraordinary costs-including document reproduction, third party copying fees, stenographic and witness expenses, and approved legal fees-while excluding ordinary administrative and overhead costs.