Indiana Code Title 22. Labor and Safety § 22-9-2-4

Sec. 4. (a) Any provision in any contract, agreement or understanding entered into on or after October 1, 1965, but before October 1, 1979, which shall prevent or tend to prevent the employment of any person solely because of the person's age, who has attained the age of forty (40) years and has not attained the age of sixty-five (65) years shall be null and void.

(b) Any provision in any contract, agreement or understanding entered into after September 30, 1979, and before July 1, 2009, which prevents or tends to prevent the employment of any person solely because of the person's age, who has attained the age of forty (40) years and has not attained the age of seventy (70) years is null and void.

(c) Any provision in any contract, agreement, or understanding entered into after June 30, 2009, that prevents or tends to prevent the employment of any person who has attained forty (40) years of age and has not attained seventy-five (75) years of age solely because of the person's age is null and void.