31 C.F.R. § 315.37 Payment during lives of both coowners.
Title 31 - Money and Finance: Treasury
A savings bond registered in coownership form will be paid to either coowner upon surrender with an appropriate request, and, upon payment (as determined in §315.43), the other coowner will cease to have any interest in the bond. If both coowners request payment and payment is to be made by check, the check will be drawn in the form, “John A. Jones and Mary C. Jones”.
Title 31: Money and Finance: Treasury
PART 315—REGULATIONS GOVERNING U.S. SAVINGS BONDS, SERIES A, B, C, D, E, F, G, H, J, AND K, AND U.S. SAVINGS NOTES
Subpart H—General Provisions for Payment
§ 315.37 Payment during lives of both coowners.

