How to register an Austrian branded sender ID
As of October 1, 2026, all businesses using a branded (alphanumeric) sender ID to send SMS messages to recipients in Austria must have their sender ID registered with Austria's telecom regulator, RTR (Rundfunk und Telekom Regulierungs-GmbH), through an Austrian-licensed SMS provider. This includes customers who have previously sent to Austrian recipients using the same sender ID. Once October 1, 2026 passes, unregistered alphanumeric sender IDs are blocked from sending.
Who needs to register
You must register if both of the following apply:
- You send SMS to recipients with Austrian phone numbers
- You use a branded (alphanumeric) sender I
If you're not sure whether your account uses a branded sender ID, check your SMS settings in Klaviyo.
Austria's sender ID format rules
Austria enforces its own character rules for alphanumeric sender IDs, separate from other countries:
- Up to 11 characters
- Must include at least 1 letter
- Allowed characters: A–Z, a–z, 0–9, space, +, -, &, _
- No umlauts or accented characters (e.g., ß, ä, ö, ü, ë, ï, ÿ)
- No space at the beginning or end of the sender ID
If your sender ID doesn't already exist, you may need to update it to meet these rules before registering.
What you'll need before you start
Each sender ID submission requires:
- Sender ID
- Company (legal entity) name
- Street address, postal code, and city
- Country code
- Company contact email address
- Justification: a short written explanation of why the sender ID is uniquely tied to your business (e.g., it matches your trade name, brand, or product). If the connection between your sender ID and business name isn't obvious, RTR requires this explanation before it will approve the ID.
- Signed Letter of Authorization: a signed letter attesting that the submitted information is accurate
Other things to know
- Rate limit: A single business may register no more than 10 new alphanumeric sender IDs within any rolling 6-month period.
Frequently asked questions
I don't plan to use my branded sender ID in Austria. Do I need to register?
No. Registration only applies if you send SMS to recipients in Austria using a branded sender ID.
I already registered my sender ID for another country (e.g., Australia or Ireland). Do I need to register again for Austria?
Yes. Austria's registry is specific to Austria and does not recognize registrations completed with other countries' regulators.
What happens if I miss the deadline?
Starting October 1, 2026, SMS messages using an unregistered branded sender ID will be blocked from delivery to Austrian recipients.
How long does registration take?
RTR requires up to 14 days to review a submission. Additional processing time applies for Klaviyo and our Austrian provider to submit the request, anticipate a total turnaround time of 21-24 days.