The ESF Regulation (Regulation (EU) No 1304/2013) sets out the following requirements for YEI reporting (Art. 19(3)): Indicator data transmitted shall relate to values for the indicators set out in Annexes I and II to this Regulation and, where applicable, to programme specific indicators. In other words, investments benefitting from YEI funding should report all common indicators listed under Annex I and all YEI indicators listed under Annex II.
Note that the reporting schedule for YEI operations differs from that of regular operations: all YEI indicators have to be reported annually already as from 2015. Representative samples of participants in YEI funded operations need to be selected in order to report on YEI longer-term result indicators on an annual basis (rather than just twice as for the ESF common indicators under Annex I).
For more information, see section 3.1.4 of the EC Guidance on Monitoring and Evaluation "Specific provisions for Common YEI indicators".