17 CFR §240.10b-21

1. (a)It shall also constitute a “manipulative or deceptive device or contrivance” as used in section 10(b) of this Act for any person to submit an order to sell an equity security if such person deceives a broker or dealer, a participant of a registered clearing agency, or a purchaser about its intention or ability to deliver the security on or before the settlement date, and such person fails to deliver the security on or before the settlement date.
2. (b)For purposes of this rule, the term settlement date shall mean the business day on which delivery of a security and payment of money is to be made through the facilities of a registered clearing agency in connection with the sale of a security.