IVR (Interactive Voice Response) services are introduced with reference to VoiceXML (Voice eXtensible Markup Language). It is explained how IVR services can benefit from an underlying formalism and rigorous analysis. IVR services are modelled using Cress(Chisel Representation Employing Systematic Specification) as a high-level graphical notation. Apart from being able to describe services, Cress also introduces the notion of features. The translation of IVR descriptions into SDL is explored, along with how the generated SDL can be formally analysed.