Transaction reporting provides regulators with fundamental data needed for market surveillance. A recent ACA Compliance Group (ACA) presentation examined the transaction reporting regimes under the E.U. Markets in Financial Instruments Directive (MiFID I) and the recast Directive (MiFID II), including enforcement activity under MiFID I; the transition to the reporting regime under MiFID II; common errors and compliance issues under both regimes; monitoring and reconciliation of reporting; and handling of reporting errors. The program was moderated by ACA director Bobby Johal and featured ACA senior principal consultants Matthew Chapman and Charlotte Longman. This article presents the key takeaways from the presentation. For more on MiFID II, see “ACA Panel Reviews Effects of Impending MiFID II on U.S. Advisers” (Dec. 7, 2017); “MiFID II Will Affect Market Structure, Registration and Soft Dollars for Hedge Funds Trading in Europe” (May 19, 2016); and our two-part series “Simmons & Simmons and Advise Technologies Provide Comprehensive Overview of MiFID II”: Part One (Jun. 18, 2015); and Part Two (Jun. 25, 2015).