This can be summarised as the safeguarding of a client’s assets.
Shares, for example, are registered securities, just like property, so it is important that the right legal owner ends up on the right register at the right time. With shares this can all be done electronically however with bearer securities, such as Eurobonds, the custodian may handle physical safekeeping too. Aside from safekeeping securities a custodian may also offer other services such as settlement (ensuring the right number of securities is legally registered in the relevant account at the right time), tax support, foreign exchange management and dividend and/or interest receipts and payments. Finally a custodian will typically manage corporate actions (share buybacks or splits) on behalf of its clients.