This message is sent by an account servicer (account servicing Institution) to an account. The account owner may be a global custodian which has an account with its local agent (sub custodian), a local agent (sub custodian) which has an account with its clearing agent or registration provider, a financial institution which has an account with its local agent (sub custodian).
This message is used to:
advise the status of a registration instruction or modification previously sent by the account owner (the function of the message is INST),
advise the status of the registration process (the function of the message is REGT),
reply to a cancellation request previously sent by the account owner (the function of the message is CAST).