N.Y.C. Admin. Code § 5-205: § 5-205 Procedure for investment of sinking fund moneys.

All obligations which shall be purchased by the comptroller with respect to the several sinking funds of the city established prior to July first, nineteen hundred eighty-one shall be transferred to the comptroller, and all transfers thereof shall be made by the comptroller. Obligations of the city which shall be purchased by the comptroller shall not be cancelled by the comptroller until the final redemption of the same, and all interest accruing therefrom shall regularly be paid to the appropriate sinking funds.