The mission of Principle 11 is to provide the framework for, where appropriate, configuring the custodian’s duties towards its contractual clients. The text is structured in 5 sections, which are followed by the Comments (from 11.1 to 11.16), which establish the obligations and duties related to private law that a custodian owes to their client, their level or degree of applicability, as well as the elements that make up a custody agreement. These aspects are critically addressed in the work: Principle 11(1) deals with the minimum mandatory duties, and Principle 11(3) relates to the initial additional duties of a custodian. However, States may decide to incorporate these duties among the mandatory duties specified in Principle 11(1). Principle 11(2) is related to using an omnibus account and the options and rules for maintaining digital assets in this context. Principle 11(4) deals with the custodian using the services of a sub-custodian to provide the custody service entrusted to it, and, finally, Principle 11(5) relates to the security rights that may exist over a digital asset held by a custodian for their client, given the impact this has on the fulfilment of their duties.