31 CFR §363.40

1. (a)Payment of a savings bond that has reached final maturity. We will purchase a zero-percent certificate of indebtedness in your TreasuryDirect ® account using the proceeds of a matured savings bond.
2. (b)Payments of interest and principal (except a savings bond that has reached final maturity).
   1. (1)We provide two methods of receiving payments of principal and interest:
      1. (i)Payment to your account at a financial institution by the ACH method, or
      2. (ii)Payment to your TreasuryDirect account to purchase a zero-percent certificate of indebtedness.
   2. (2)You may select different payment destinations for principal and interest for a marketable Treasury security. You may change your payment destination at any time, unless the security is in the closed book period. (See § 363.210.)
   3. (3)If we are unable to deliver a payment, we will use the payment to purchase a zero-percent certificate of indebtedness in your TreasuryDirect account.