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Documents Required and Instructions to Register Your Alphanumeric Sender ID with a hash (#) prefix in Hong Kong.

Before we begin

The Office of the Communications Authority (“OFCA”) issued the “Guidelines on Registration of Sender IDs and Sending of Short Messages and Multimedia Messages” (“Guidelines”) in October 2023 (revised in February 2024) to implement the SMS Sender Registration Scheme ("Scheme") from 28 Dec 2023. The Guidelines set out the requirements for registration of Sender ID(s) with the prefix # to be used for sending SMS to local subscribers of mobile services in Hong Kong through registered SMS service providers. Under the Scheme, a participating company or organisation applies to OFCA to become a Registered Sender, and registers its SMS Sender ID(s) with the prefix "#". The relevant registrations are recorded in the SMS Sender Registry ("Registry") established by OFCA for public information. 

Only companies or organisations which are Registered Senders are able to send SMS messages using their registered SMS Sender IDs with the prefix '#'. All other SMS messages with sender IDs containing '#' but not sent by Registered Senders will be blocked by the telecommunications networks. With such an arrangement, members of the public can easily identify whether an SMS message is received from a Registered Sender by the prefix "#" in the SMS Sender ID.

Companies or organisations interested in joining the Scheme may visit OFCA's website for details and submit their completed application forms together with the required information to OFCA. OFCA will review the application and the SMS Sender ID(s) that can be used for registration if the application is approved

Please note that this does not impact SMS messages sent from Hong Kong domestic long codes. After registering with OFCA, you need to register it with Twilio using the console.



To register your Alphanumeric Sender ID, the Hong Kong network operators require that you provide the following documents: 

  • Letter of Authorisation (LOA)-LOA to RSSP CITIC
  • Letter of Authorisation (LOA)-LOA to RSSP PCCW
  • Letter of Authorisation (LOA)-LOA to RSSP SmarTone
  • Letter of Authorisation (LOA)-LOA to China Mobile
  • Letter of Authorisation (LOA)-LOA to Twilio
  • Business Licence
  • Proof of registration that the Sender ID with # has been registered with OFCA

To get you up and running as quickly as possible, please fill out the document completely and accurately and provide any other required information. Use the examples provided for guidance. Note that mobile network carriers are very strict about the details! We highly recommend that you download the examples (hit right click, and select 'Save Image As...') and do a side by side comparison when you are filling out the documents.

Once you have downloaded the forms, follow these general instructions: 

  1. Fill in the yellow highlighted fields—completely replace each field with your own information. If a field is not highlighted, don’t change it.
  2. All LOAs to CITIC, PCCW, SmarTone and China Mobile have the same format with the only difference being who it is addressed to.
  3. If you have questions on how to fill in the required fields, refer to the annotated examples we provided for each field. 
  4. Have the documents signed by an authorised signatory of the Sender.
  5. In the yellow highlighted fields, add the Sender’s letterhead and/or logo, and sign where indicated.
  6. Upload the forms to the console.

LOA to RSSP CITIC, PCCW, SmarTone and China Mobile

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Screenshot 2023-11-21 at 12.16.46.png

LOA to Twilio

Screenshot 2023-11-21 at 12.26.25.pngScreenshot 2023-11-21 at 12.41.27.png

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