Non-tariff measures (NTMs) play a crucial role in shaping international trade. While tariffs remain important instruments of trade policy, NTMs increasingly play a prominent role in determining market access and trade costs. According to UNCTAD, NTMs tend to have a significantly greater impact on trade costs than tariffs. Thus, NTMs may - even unintentionally - act as barriers to trade. Moreover, they often serve legitimate public policy objectives, such as protecting health, safety and the environment. Unlike tariffs, which are relatively straightforward to quantify—typically expressed as a percentage of the product’s value or in monetary terms—NTMs are inherently more complex. They encompass a wide range of regulatory measures, including product requirements, health and safety regulations, and import quotas, whose trade effects are not easily measurable. Their administration is often fragmented across multiple government agencies, further complicating transparency and analysis. Tariffs are more transparent, as countries generally publish and communicate their tariff schedules to the public and World Trade Organization. As NTMs continue to grow in importance, understanding their nature, incidence, scope, implementation, and impact on trade is essential for policymakers, researchers, and stakeholders engaged in global trade. This guideline presents possible analytical approaches used to support policymakers in understanding and designing regulations that minimize costs to trading businesses while maintaining important public policy objectives. This document focuses on methodologies that can be used to assess the impact of NTMs on trade and development.