This brief presents an approach to assessing the cost impacts of GBV on businesses. The approach is adjusted from a methodology created by Duvvury et al. (2004) but also draws upon previous studies that specifically examined existing methodologies and strategies for costing GBV impacts (Williams, 2014; Day et al., 2005; Duvvury et al., 2004). Based on these reviews, as well as applied experience in Papua New Guinea (Darko et al., 2015), the costing methodology and tools consist of four core steps: a framing of GBV definitions and scope; partnership development and collection of background data; fieldwork and feedback; and a cost-calculation and presentation phase. These four components are addressed in detail in the document. Each consists of several methodological subcategories that depend on the broader implementation environment, the business sector context and the type and capacity of the actors undertaking the costing activity. The latter issues are addressed after discussion of the core tool, and a case study provides a brief overview of the costing process in action.