Enterprise Resource Planning (ERP) Systems are standardized software packages intended to support the majority or all of an organization's processes. Customization of an ERP system is usually required to achieve fit between system and business processes of an organization. Customization options ranges from setting parameters in the system to developing new functionality by modifying source code. Models describing customization options are a decade old. Since then, the trend is for ERP systems to become more flexible. The feasibility of customization is facilitated and new options for customization are made available. Through in depth interviews, this research identifies a need for revising existing models. Presents necessary changes and proposes new customization options that should be included in a new model. There is also a need for customization models for different types of ERP systems. This paper therefore also contributes with describing how customization of cloud ERP relates to existing models.