N.J. Stat. § 40:3-20
If upon any tabulation heretofore made of outstanding term bonds and the calculation to determine whether the sinking fund for each issue is equal to the amortization basis set forth in section 40:3-16 of this Title, or upon any subsequent tabulation and calculation ordered by the Director of the Division of Local Government in the State Department of Taxation and Finance, the sinking fund for any issue of term bonds of any municipality, county or school district shall be found to be in excess of the proper amortization basis, and any other sinking fund shall be found to be deficient, such excess shall be transferred and credited to the deficient sinking funds.
Where a distribution of surpluses is made, it must be first made to the sinking funds for bonds within the classification as defined in section 40:3-12 of this Title, and then to the sinking funds for other bonds in the order of their maturities.
Should there be a surplus in the sinking fund after the distribution herein directed, the same may be transferred to a surplus account, and the principal thereof shall be distributed only as provided in sections 40:3-13 and 40:3-24 of this Title.
N.J.S. § 40:3-20