This handbook responds to the Meeting of the Parties Decision IX/28, which requested the United Nations Environment Programme to prepare a handbook to assist all parties with fulfilling their data reporting obligations under the Montreal Protocol. It helps ozone officers understand and follow the correct data reporting procedures, including those related to Article 7 and Multilateral Fund requirements. Although specifically written for National Ozone Units in Article 5 countries, the handbook will also be useful for Article 7 data reporting by non-Article 5 countries.