The Service-Oriented Architectures (SOA) are increasingly used in various application domains. Nowadays various Services operate on the Web and access various critical resources such as databases. These services are called transactional web services when they perform transactional actions. This kind of Services must verify the relevant constraints related to transactional systems. In our work, we focus on web services described with BPEL [1]. In the BPEL language, a composite Web Service is implemented by a process that consists of activities such as the messaging activities invoke and reply, used for interacting with other web services and the structured activities sequence, flow and scope, acting as containers for their nested activities. BPEL provides some support for transactions through its fault and compensation handlers undoing the effects of completed activities. In most related work [2,3], validation of the web services composition and workflow shows how to model transactional behaviors and involves the verification of behavioral properties. In our work, we sketch a methodology showing how Event B models [4,5] obtained by the approach described in [6] can be used to prove web services transactional properties. Transactional services that access and manage critical resources are isolated in a scope element with compensation and fault handlers. When modelling fault and compensation handlers by a set of events, it becomes possible to model and check the properties related to transactional web services. These properties are encoded in the INVARIANTS clause in order to guarantee consistency of the manipulated resources.