Read your Operating Limitations. The below paragraph (28) is from the standard "Operating Limitations" for Special, Experimental, Amateur Built aircraft, imposed on DARs and ASIs by FAA Order 8130.2 when issuing airworthiness certificates. So there is a requirement, assuming you have this limitation, and you are flying into or out of an airport with a control tower. Most but not all pilots carry this over into uncontrolled fields.
b. The following operating limitations SHALL be prescribed to experimental amateur-built aircraft: ... (28) The pilot in command of this aircraft must notify air traffic control of the experimental nature of this aircraft when operating into or out of airports with an operational control tower. When filing IFR, the experimental nature of this aircraft must be listed in the remarks section of the flight plan. Ken Jones
