The present document specifies requirements for relay services provided over ICT networks. It is intended to give information suitable for incorporation into contracts between commissioning agents and relay service providers. The present document is applicable to all kinds of relay services which enable a user with functional limitations related to hearing@ vision@ speech or cognitive functions@ or combinations thereof@ to converse with other users. The present document applies to text relay services@ speech-to-speech relay services@ video relay services@ and captioned telephony services. Requirements are specified for services provided on a 24/7 basis@ as well as for limited-hour services. The present document does not place requirements on network operators.