31 CFR §357.29

For purposes of a transaction request affecting payment instructions with respect to a security, a proper request must be received not less than ten (10) business days preceding the next payment date. If a transaction request is received less than ten (10) business days preceding a payment date, the Department may in its discretion act on such request if sufficient time remains for processing. If a transaction request is received too late for completion of the requested transaction, the transaction request will be acted upon with respect to future payments only.