363.40—How are payments of principal and interest made?
        
        (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.
    
    
        
        (b) Payments of interest and principal (except a savings bond that has reached final maturity).
        
        (1) 
         We provide two methods of receiving payments of principal and interest:
    
    
    
    
        
        (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) 
         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.