When are you required to transmit your assigned call sign?

The fundamental rule for station identification in the amateur radio service is transmitting your FCC-assigned call sign at least every 10 minutes during an ongoing contact, and at the very end of the contact. Many new operators mistakenly believe they must identify at the beginning of a contact. While it is standard operating practice and good etiquette to state your call sign at the start of a transmission so the other station knows who is calling, the FCC rules only legally mandate the 10-minute intervals and the end of the communication.