Recognizing the need to update the original version of the Guidelines to reflect changing practices, IPIECA and API jointly initiated the development of this second edition of the Guidelines to continue to promote credible, consistent and reliable greenhouse gas (GHG) accounting and reporting practices from oil and gas operations. As with the original, these guidelines are based on the WRI/WBCSD GHG Protocol, but add (and occasionally differ) by providing industry-specific guidance. The new edition holds significantly revised chapters on setting boundaries (including discussion of financial control and clearer reference to Scope 1, 2, and 3 emissions) and the evaluation of industry GHG emissions, including uncertainty. There are also revisions to discussions around reporting emissions over time, de minimis emissions, and normalization. The revised Guidelines have aimed to achieve consistency with the approaches described in the revised IPIECA/API/OGP publication Oil and gas industry guidance on voluntary sustainability reporting.