19 Net revenue Net revenue breaks down into the following revenue categories: (XLS:) Download millions of € 2018 2017b 2016b a Revenue from the sale of goods and merchandise includes interest income of EUR 0.3 billion in the reporting period, calculated using the effective interest method. This income is primarily attributable to accrued interest on receivables in connection with handsets sold under installment plans in the United States operating segment. b Prior-year figures were adjusted retrospectively on account of a change in the allocation between revenue categories. Revenue from the rendering of services 61,942 62,448 61,163 Germany 17,657 18,382 18,453 United States 27,755 27,232 25,588 Europe 9,883 9,937 9,925 Systems Solutions 5,328 5,413 5,532 Group Development 1,257 1,374 1,450 Group Headquarters & Group Services 63 110 215 Revenue from the sale of goods and merchandisea 12,443 11,079 10,063 Germany 2,208 1,735 1,569 United States 8,170 7,714 6,869 Europe 1,588 1,236 1,141 Systems Solutions 154 90 145 Group Development 322 286 294 Group Headquarters & Group Services 0 18 45 Revenue from the use of entity assets by others 1,271 1,420 1,869 Germany 486 436 383 United States 596 789 1,280 Europe 51 45 45 Systems Solutions 15 0 0 Group Development 0 0 0 Group Headquarters & Group Services 123 150 161 NET REVENUE 75,656 74,947 73,095 The total transaction price attributable to performance obligations that have not been fulfilled or, in some cases, not yet fulfilled at the end of the reporting period (hereinafter: outstanding transaction price) amounts to EUR 18,323 million. The portion of the outstanding transaction price attributable to performance obligations that have not been fulfilled or, in some cases, not yet fulfilled at the end of the reporting period is generally recognized as revenue over the remaining term of the service contracts concluded. Since most service contracts – insofar as they are not able to be terminated at any time – have a minimum contract term of 24 months, an average remaining term of approximately 12 months can be assumed, provided the course of business in the mass business remains virtually unchanged. The disclosures only refer to transactions within the scope of IFRS 15, i.e., they do not include portions of the transaction price being allocated to performance obligations outside the scope of the standard, e.g., leases. Deutsche Telekom generally makes use of the practical expedients in IFRS 15, according to which outstanding performance obligations under contracts with an expected original term of no more than one year and revenues recognized in accordance with the billed amounts are exempt from the disclosure requirement. Individual subsidiaries deviate from this general approach and have not made use of these practical expedients for similar contracts. For further information on changes in net revenue, please refer to the section “Development of business in the Group” in the combined management report. Service concession arrangements Satellic NV, Machelen, Belgium, is a fully consolidated subsidiary of Deutsche Telekom and on July 25, 2014 signed a contractual arrangement with Viapass, the public agency responsible for toll collection in Belgium, for the set-up, operation, and financing of an electronic toll collection system. After Viapass accepted the system on March 30, 2016, the set-up phase was completed on March 31, 2016. The operation phase that follows will have a duration of twelve years, with the additional option for Viapass to extend the term three times by one year. Satellic has no entitlement to the toll revenue collected but will receive contractually agreed fees for setting up and operating the system. Viapass is authorized to terminate the arrangement giving notice of six months with payment of reasonable compensation. In the event of regular or premature termination of the agreement, Satellic has an obligation to hand over to Viapass, on request, material assets for the operation of the toll collection system that have not yet passed to the ownership of Viapass; in such an event, however, the software platform for toll collection would not be handed over to Viapass. The agreement was classified as a service concession arrangement within the meaning of IFRIC 12. Since the start of the operation phase on April 1, 2016, the separate fees for operation and maintenance services have been recognized as revenue in the respective periods, which totaled EUR 67 million in the reporting year (2017: EUR 75 million, 2016: EUR 68 million).