# 13223: Dial: Invalid phone number format Log Type: APPLICATION Log Level: WARNING ## Description Phone Numbers must be in E.164 format. E.164 numbers are formatted \[+] \[country code] \[subscriber number including area code] and can have a maximum of 15 digits. ### Possible causes * The phone number you are attempting to dial is not in E.164 format * The `` noun inside your `` TwiML instructions is not present * You are attempting to dial something that is not a phone number ### Possible solutions Check the format of the phone number inside your `` TwiML. Verify that the number is in [E.164 format](/docs/glossary/what-e164): * Includes the country code * Includes the area code * Does not exceed 15 digits * Does not include any invalid characters, like hyphens or parentheses In your TwiML instructions, the phone number must be between the opening and closing `` tags, which are nested within ``'s opening and closing tags: ```bash +15555555555 ``` If you are attempting to `` an SDK end-user, ensure you're using the `` noun inside your `` tags. If you are attempting to `` a SIP endpoint, ensure you're using the `` noun inside your `` tags. For more information, read the [`` docs](/docs/voice/twiml/dial).