17 CFR 270.17f-3: f-3 Free cash accounts for investment companies with bank custodians.

No registered investment company having a bank custodian shall hold free cash except, upon resolution of its board or directors, a petty cash account may be maintained in an amount not to exceed $500: Provided, That such account is operated under the imprest system and is maintained subject to adequate controls approved by the board of directors over disbursements and reimbursements including, but not limited to fidelity bond coverage of persons having access to such funds.