N.Y.C. Admin. Code § 13-538: § 13-538 Fund for current needs.

For the purpose of meeting disbursements for pensions, pensions-providing-for-increased-take-home-pay, annuities and other payments in excess of the receipts, there may be kept an available fund, not exceeding ten per cent of the total amount in the several funds provided for by this chapter, on deposit in any bank in this state, organized under the laws thereof or under the laws of the United States, or with any trust company incorporated by any law of this state, provided such bank or trust company shall furnish adequate security for such funds and provided that the sum so deposited in any one bank or trust company shall not exceed twenty-five per cent of the paid-up capital and surplus of such bank or trust company.