For both hydrocarbon and geothermal resource exploitation and in deployment of CCS, delivering safe and effective wells is a vital and necessary activity. The scale and complexity of the well planning and design process is dependent on many factors including organizational policy, relevant experience, environment of selected well location, prognosed subsurface conditions and associated uncertainties and the well objectives. Wells types, associated costs and risk exposure vary enormously from high-cost uncalibrated deep-water wild-cat HPHT exploration targets through to highly-calibrated, low complexity, shallow land-based vertical NPNT hydrocarbon and geothermal wells. In the former case, well planning and design effort is typically complex, resource intensive and tailored to accommodate and cater for both challenging surface and subsurface environmental conditions and relatively large uncertainties. In the latter case, surface and subsurface environments present fewer challenges and the planning and design phase may leverage tried and tested well designs, significantly reducing the need for an extensive well planning and design process. However, in all cases, deliberate choices should be made w.r.t. an appropriately scaled well planning and design process, which should be contain agreed decision gates to support good business decisions and safe, effective and competitive well design to meet the well objectives.