250. In terms of the validation rules, the underlying should be identified by using a unique identification for this underlying based on its type. Fields 2.13-2.18 describe the underlying, and the field 'Underlying identification type' in particular indicates that the underlying is either a basket, index or asset identified with an ISIN.

251. ESMA encountered issues with the reporting of underlying ID for derivatives on indices given that some counterparties report the ISIN of the underlying, whilst other counterparties report the ISIN of the derivative. In this respect, ESMA clarifies that for these instruments, counterparties should report ISIN of the underlying index if it is available. In addition, under the draft RTS on reporting the counterparties should report the standardised code indicating the index (if available) as well as the name of the index.

Q43. Do you require any further clarification on the reporting of details of the underlying?