Austria’s Regulatory Authority for Broadcasting and Telecommunications, Rundfunk und Telekom Regulierungs (RTR), is requiring that all Alphanumeric Sender IDs be registered in a national registry.
Starting October 1, 2026, any messages using Sender IDs that aren’t registered with RTR will be blocked with error code 21612. In this article, you’ll find the specific documentation you’ll need to submit, what to expect after submission, and answers to common questions.
RTR has informed us that there may be up to a 2-week turnaround time on registrations being approved. As such, we recommend that you register your Sender IDs at the latest by September 15, 2026.
Required information to Register your Sender ID
To register a Sender ID, we need information about the business or entities, a business representative, and proof that the Sender ID relates to your business or brand.
You need to register and provide all supporting documentation through the Twilio Console. You can begin your registration and come back to it as required.
1. The Sender ID
Sender IDs in Austria are treated case sensitive, as such case sensitive permutations intended for use should be registered separately (e.g., “ABC”, “Abc”, “abc”). Additionally, the following limitations apply:
- Length: 1 to 11 characters
- Permitted characters: A-Z, a-z, 0-9, spaces, +, -, &, _
- No umlauts, no ß
- No leading/trailing spaces
- No generic identifiers (e.g., “dentist”)
2. Business/entity information
- Legal Business Name
- Business address
- Business phone number
- Business registration number (most typically a country Tax Identification Number such as EU VAT ID)
- Company website (needs to be active)
- Business Representative Name
- Business Representative Email Address
If you are an Independent Software Vendor (ISV) and registering a Sender ID on their behalf, you will need to provide the information of your end business customers.
3. Authorized Representative
You’ll need to name an Authorized Representative who can act on behalf of your business for this Sender ID registration via Twilio. You will need to upload an official government ID of the named Authorized Representative.
You’ll need:
- Authorized Representative Name
- Authorized Representative Email Address. This must be a corporate email address, matching the Authorized Representative’s name (“freemail” addresses such as Gmail, Yahoo, are not acceptable)
- A government-issued photo ID of the Business Representative
If you are an ISV, you will need to have the government ID of your business customer’s Authorized Representative when you begin your registration process in the Twilio console.
4. Sender ID and Proof of Brand Connection
For each Sender ID you want Twilio to register, you’ll need to provide the proof of your need to use the Sender ID being registered. You will be prompted to select one of the following:
- Company Registration: The requested Sender ID matches the name on my official company registration
- Domain: The requested Sender ID matches my domain name
- Trading name: The requested Sender ID matches the trading name of my company
- Trademark/Brand: The requested Sender ID matches my protected trademark/brand
If 3 or 4 is selected, you must also provide additional evidence of the linkage to the Sender ID being registered. Examples may include additional URLs that show the linkage to the Sender ID, or an explanation of your businesses' Trading Name and its relation to the Company name. You may also upload a document that contains proof of your trademark or trading name.
What happens after your information and documents are submitted on Twilio Console
Once you submit your documents and information on Twilio Console, we’ll review everything and reach out if we need more information. If your information checks out and your Sender ID meets RTR’s requirements, we’ll register the Sender ID to RTR’s registry.
After RTR approves your application, we’ll set up the Sender ID for your account (and any additional accounts that you’ve indicated) and let you know when it’s ready to use. Once this is done, after October 1 2026, your messages will not be subject to any blocking.
FAQs
Do I need to register each Sender ID separately?
Yes. Each unique alias requires its own registration with the RTR.
What happens if my Sender ID isn’t registered before October 1, 2026?
Your messages using unregistered alphanumeric sender IDs will be blocked with the error code 21612. They will not be delivered.
I'm an ISV with many customers using Sender IDs. What do I need to do?
Each Sender ID used by your customers must be registered separately. You must provide your customers’ business and representative information, including a government ID for verification.
Can I register my Sender ID directly with RTR?
No, you must register through a provider of mobile, number-based interpersonal communication (“NBICS”) services, such as Twilio.
I registered my Sender ID with another provider. Do I have to register again with Twilio?
Yes. While the Sender ID may be approved for use in the RTR portal, Twilio still has to verify your business identity and your right to use the Sender ID.
What is the difference between the Business Representative and the Authorized Representative?
The Business Representative is part of your Twilio’s compliance profile. This person may or may not be the person that you want to be your Authorized Representative for this particular Sender ID registration. The Authorized Representative is the person whose government ID will need to be verified. They are allowed to be the same person.
I would like to register my sender ID to be used in multiple Twilio accounts. What do I need to do?
During the registration process, you will be asked if you would like to include all of your associated subaccounts as part of your Sender ID registration. If you indicate as such, all of your current existing subaccounts (associated with the account that you are registering in) will be automatically configured with the registered Sender ID upon approval. If you would like the Sender ID to be registered in multiple parent Account SIDs, you will need to repeat the registration process within that account.