(3)The European Securities and Markets Authority (ESMA) and competent authorities may need to request data on an ad-hoc basis from trading venues, APAs and CTPs as part of their assessment of the pre-trade and post-trade transparency and the trading obligation regimes. To allow for efficient data delivery and for consolidation with similar data from other sources, ESMA and competent authorities should, in the case of ad-hoc data requests, be able to specify the format in which the data should be submitted. To minimise burden for market participants, ESMA and competent authorities should rely as much as possible on existing datasets, including transaction data reported in accordance with Article 26 of Regulation (EU) No 600/2014, and resort to ad-hoc data requests only where necessary.