Which transactions can sometimes be passported under the ancillary MIFID regulation?

The correct answer highlights that safekeeping and custodial services can sometimes be passported under the ancillary MiFID regulation. This regulation allows firms that provide certain activities closely related to investment services to have the benefit of EU-wide passporting rights, meaning they can offer services across Europe without needing to establish a separate local presence in each Member State.

Safekeeping and custodial services are integral to many financial services as they involve holding or safeguarding client assets. These functions complement investment activities, making them a suitable candidate for passporting under MiFID's ancillary provisions. As such, firms specializing in these services can leverage this regulatory flexibility to expand their operations across EU jurisdictions efficiently.

In contrast, underwriting advice, insurance and hedging activities, and credit derivatives do not typically fall under the same regulatory framework or the specific ancillary services defined by MiFID. While these activities play important roles in the financial market, they have different regulatory implications and are often subject to separate directives and requirements, which limit their ability to be passported in the same manner as custodial services.