Digital Asset Custody and Banking: How Institutional Custodians Interface with Traditional Finance

Institutional digital asset custodians — firms that safekeep private keys on behalf of institutional clients — sit at the intersection of traditional financial regulation and the digital asset ecosystem. Whether regulated as trust companies (Coinbase Custody, BitGo Trust), as authorised investment firms (Copper, Komainu), or under MiCA's CASP framework, custodians must maintain sophisticated banking infrastructure to handle client fiat flows alongside their core custody operations.

Regulatory Framework for Institutional Custody

In the UK, digital asset custody may constitute safeguarding and administering investments if the assets held meet the definition of a specified investment under FSMA 2000. The FCA has indicated that certain crypto assets — particularly those with investment characteristics — may fall within this definition, requiring full FCA authorisation rather than simple MLR registration. Custodians operating in uncertainty regarding the regulatory classification of their assets should obtain a Binding Guidance Request from the FCA.

Under MiCA Article 70, CASP custodians are required to maintain a strict segregation between client assets and their own proprietary assets. Client crypto assets must be held in segregated wallets identifiable by client, and client fiat balances must be held in segregated accounts at credit institutions. These requirements align with the UK's Client Asset Sourcebook (CASS) principles applied to traditional investment firms and represent a significant operational infrastructure requirement for custodians building MiCA-compliant operations.

In the United States, qualified custodians for digital assets include NYDFS-chartered trust companies (Coinbase Custody, Paxos, BitGo) and federally chartered banks with OCC-approved digital asset custody programmes. The SEC's Staff Accounting Bulletin 121 — which required public companies to record crypto assets held on behalf of clients as both an asset and liability on their balance sheet — was rescinded in early 2025, removing a significant capital deterrent to bank participation in digital asset custody.

Fiat Settlement Infrastructure

The fiat side of a custody operation handles: client fiat deposits prior to crypto purchase, fiat proceeds from client crypto sales, custody fee payments, and operational expenses. Each of these flows has different compliance characteristics and requires specific banking infrastructure.

Client fiat deposits prior to crypto purchase must be held in segregated client money accounts under the applicable framework (CASS 7 in the UK, MiCA Article 70 in the EU). These accounts must be held at credit institutions rather than at the custodian itself, creating a dependency on traditional banking relationships for client money safekeeping. For custodians managing institutional clients with large position sizes, the volumes can be substantial — requiring banking partners with the balance sheet and transaction limits to accommodate multi-hundred-million-dollar client money pools.

Proceeds from client asset sales present a different challenge: large, irregular fiat receipts originating from exchange sales or OTC desk settlements that must be attributed to specific client accounts and disbursed promptly. The custodian's banking partner must be able to process these receipts, attribute them correctly, and enable same-day or next-day disbursement to client bank accounts. Transaction monitoring at the banking partner level will scrutinise the large, irregular nature of these flows, requiring the custodian to maintain detailed transaction justification documentation.

Multi-Jurisdiction Banking for Global Custodians

Custodians serving global institutional clients need banking infrastructure in multiple jurisdictions to facilitate settlement in clients' local currencies. A US-based pension fund buying ETH through a UK-based custodian needs USD settlement; a Swiss family office needs CHF; a Singapore sovereign wealth fund needs SGD. Multi-currency banking infrastructure with real-time FX capability is not simply a convenience — it is a competitive differentiator and a prerequisite for serving certain institutional client types.

Named IBANs in each relevant jurisdiction allow custodians to accept client fiat deposits cleanly — with the payment clearly attributable to a specific client account — rather than using pooled accounts that require complex reconciliation. The named IBAN approach also satisfies regulatory requirements for client money segregation more clearly than pooled structures, reducing compliance risk for the custodian itself.