In the ITIL Service Portfolio, Retired Services are those that are in the process of being discontinued, before they are finally decommissioned. An often overlooked element of the Service Transition stage is the phasing out of certain services while they still comprise as an element of the Service Portfolio they are not a visible component in the same way that in production services are. Retired services show services that were once in live operation but have become obsolete or are no longer profitable. Retired services are maintained because market conditions might change and a service that was once obsolete might be needed again. Retired services are the past.
While services that have been retired do not directly affect the interaction between operational service and those in the design pipeline, learnings can be taken from retired services to optimize new or upgraded services in the service pipeline.
The figure below illustrates where the Retired Services fit in the Service Lifecycle.
source: ITIL News