[ESMA 70-872942901-38 MiFID II MiFIR market structures Q&A, Q&A 3.34]

When firms use third party systems offering algorithmic trading functionalities, they are ultimately responsible for compliance with the relevant requirements in Article 17 of MiFID II and RTS 6, as specifically detailed in Article 4 or RTS 6. However, lacking direct control over the system, its operation and the algorithms deployed, these firms might not be materially able to ensure that all requirements are met.

In such instances, firms can ensure compliance with those technical requirements that cannot be otherwise met by the firm itself through contractual arrangements with the system provider, where the latter commits to ensure that the system, its operation and the algorithms deployed are compliant with the relevant legal requirements.