Twilio requires that all Short Code applications be submitted with an attached Letter of Authorization (LoA) signed by a representative from the company whose brand will appear in the short code SMS.

{BRAND LETTERHEAD}
{DATE}
Short Code Letter of Authorization

To whom it may concern,

This letter confirms that we, {BRAND NAME}, are granting Twilio permission to apply for
a short code under {SMS PROGRAM NAME} on our behalf.

If additional information is needed, please contact shortcodes@twilio.com

Regards,
{NAME AND TITLE OF BRAND REPRESENTATIVE}
{DATE}
{SIGNATURE OF BRAND REPRESENTATIVE}

A sample template is also available for download below.