Definition
AUC is an initialism standing for "assets under custody." It refers to the total market value of assets held by a custodian — typically a bank, trust company, or financial institution — on behalf of clients, but over which the custodian does not exercise investment discretion. The custodian holds legal title or safekeeping responsibility for the assets, processes transactions, and performs administrative functions, but the investment decision-making authority remains with the asset owner or a separately appointed investment manager.
AUC is a measurement and reporting metric widely used in financial services, securities law, and fiduciary compliance contexts. It is distinct from assets under management (AUM), where the manager holds discretionary authority over investment decisions.
Common Confusion
AUC is frequently confused with AUM (assets under management). The distinction is legally material: AUM implies discretionary investment authority and typically triggers a higher tier of fiduciary duty. AUC implies a safekeeping and administrative role without investment discretion. A document reporting high AUC figures for an institution does not establish that the institution is making investment decisions over those assets.
A secondary confusion arises with AUA (assets under administration), which is sometimes used interchangeably with AUC but can refer to a broader administrative service relationship that may or may not include physical custody of the assets themselves.
Why It Matters in Research
AUC as a formal initialism does not appear in historical legal dictionaries, including Burrill's, which predates the modern custodial securities industry by several decades. Researchers working with pre-twentieth century sources will find no entry for this term, and its absence from historical sources is not an editorial gap — it reflects a genuinely modern usage tied to institutional securities custody, regulatory reporting frameworks, and financial industry standardization.
The term gains legal significance primarily through regulatory and fiduciary contexts: securities regulations governing custodians distinguish custody from management precisely along the AUC/AUM line. This distinction matters when researching broker-dealer obligations, investment adviser rules, bank trust department responsibilities, and safe custody agreements. Conflating custodial and managerial roles in source materials — especially older trust and estate documents — can create interpretive problems when the AUC/AUM distinction is legally operative.
Researchers should be alert to the fact that "custody" in the AUC sense carries specific legal content: a custodian owes duties of safekeeping, recordkeeping, and settlement but generally does not owe the full spectrum of fiduciary investment duties attached to a discretionary manager. Sources that use "custody" loosely may obscure this boundary.
Historical Dictionary Support
Burrill's Law Dictionary does not contain an entry for AUC, and the fragment retrieved from Burrill's in the source material is misfiled — it concerns attornment and attorney-related terms, with no bearing on assets under custody. Researchers should treat the Burrill's source as silent on this term.
The broader concept of custody over property on behalf of another has deep roots in trust law and bailment doctrine, both of which are well-represented in historical dictionaries. Burrill's and similar nineteenth-century sources address "custody" in its property and personal (custodial arrest) senses, but the application to institutional securities holding as a distinct legal function and reportable metric is a product of twentieth-century financial regulation. The gap between historical coverage and modern usage is complete here — no synthesis across shelf sources is possible for AUC specifically.
Jurisdictional Note
In the United States, custodial obligations are shaped significantly by SEC rules governing investment advisers and broker-dealers, as well as state banking and trust law. In the United Kingdom and EU jurisdictions, custodian duties are addressed under financial services regulatory frameworks. The core AUC concept is consistent across major financial jurisdictions, but the specific legal duties attached to the custodial relationship vary by regulatory regime.