This paper examines the wide variety of international agreements that are currently used by host governments when granting rights to explore for, develop, produce and market hydrocarbons. The variation in fiscal terms found in these agreements covers a broad spectrum. In addition, their structures are often very complex making comparison of alternative project opportunities difficult. The key differences in the agreements and approaches that are commonly used to compare different fiscal regimes are discussed. Case examples are used to illustrate the techniques used to model and perform economic evaluations of specific agreement types and terms. Commonly used definitions and accepted practice for the determination and classification of hydrocarbon volumes are presented. Host and home government regulations that govern and establish the criteria for external reporting of reserves and related financial information are also discussed in contrast with internal reporting needs for technical and business planning purposes.