[Home](./index.md) > [sip.js](./sip.js.md) > [OutgoingRequestMessageOptions](./sip.js.outgoingrequestmessageoptions.md) > [callId](./sip.js.outgoingrequestmessageoptions.callid.md) ## OutgoingRequestMessageOptions.callId property Signature: ```typescript callId?: string; ```