Why custody matters
The day a regulator or court asks "where is the customer's money?", custody is the answer. Custody is the legal and operational regime that says: this asset belongs to the customer, not to the firm; the firm is holding it in a way that is auditable, segregated, and producible on demand; and if the firm goes bankrupt, the asset doesn't enter the firm's estate.
That is a much taller bar than "we have a database row that says she owns 0.4 BTC."
When to think about it
You think about custody when you hold any asset (cash, security, token) on a customer's behalf — directly or indirectly via a middleware. The SEC's Custody Rule, the Bank Secrecy Act, and state money-transmitter regimes all impose specific custody obligations. Crypto custody adds yet another layer: qualified custodians, MPC and HSM controls, and asset segregation on-chain.
Common pitfalls
- Commingled funds. Funds pooled with operating cash are not in custody; they are a creditor claim.
- "Custody" by sub-ledger only. A middleware sub-ledger that says you own X is not legal custody if the actual asset is comingled at the sponsor.
- Unclear bankruptcy isolation. If the custodian fails, can the customer reach the asset directly? If not, you don't really have custody.
Custody is one of the few words in fintech that means exactly what regulators say it means.