31 C.F.R. § 363.145
May I delete a pending transaction involving a zero-percent certificate of indebtedness?
(a) You may delete a pending purchase of a zero-percent certificate of indebtedness initiated from your TreasuryDirect ® account.
(b) You may delete a pending purchase of a security using a zero-percent certificate of indebtedness as payment.
(c) You may not delete a pending redemption of all or part of the value of a zero-percent certificate of indebtedness.