Rule 18f-3 (17 CFR 270.18f-3) under the Investment Company Act of 1940, Multiple class companies

Rule 18f-3 permits a registered open-end management investment company to issue multiple classes of shares representing interests in the same portfolio of securities if the fund satisfies the conditions of the rule. Each class must differ in its arrangement for shareholder services or distribution or both. Among other requirements, the fund's board of directors must approve a written plan describing the differences among classes.

The latest form for Rule 18f-3 (17 CFR 270.18f-3) under the Investment Company Act of 1940, Multiple class companies expires 2021-04-30 and can be found here.