N.Y. Comp. Codes R. & Regs. tit. 3 § 22.6
For the purpose of admissions to and withdrawals from the common trust, fund, the principal of the fund shall be determined by adding to the value of the investments, as determined in accordance with the provisions of sections 22.4 and 22.5 of this Part, the uninvested cash principal and other items of principal, and by deducting from the total thereof any liabilities, due or accrued, chargeable to principal. For the purpose of computing the value per unit, the principal thus determined shall be divided by the number of existing units and such unit value together with a sum equal to the proportionate share of any income held or accrued and remaining undistributed at the valuation date shall be the basis for admissions to and withdrawals from the common trust fund. In determining the value of a unit, fractions less than.01 percent of the original unit value may be omitted. No participation shall be admitted to or withdrawn from a common trust fund except on the basis of such valuation. A reasonable period, not to exceed five bank business days, following the completion of each valuation may be used to make the computations necessary to determine the value of the fund and of the participations therein. No participation shall be admitted to or withdrawn from a common trust fund unless a written request for or notice of intention of taking such action shall have been entered in the records of the trust company and approved by the trust investment committee.
N.Y. Comp. Codes R. & Regs. Tit. 3 § 22.6