How to Activate or Deactivate Your Alphanumeric Sender ID

Last updated at:


Alphanumeric sender IDs are the only sending numbers available in the UK and Australia. These number types allow you to choose your sender ID, making it easy to brand your SMS messages. 

In this article, we go over how to edit and turn off your alphanumeric sender IDs in Klaviyo.

About Alphanumeric Sender IDs

When you choose an SMS plan, you automatically get one free alphanumeric sender ID. 

Unlike other SMS sending numbers, the alphanumeric sender ID can be branded to reflect who the message is coming from, similar to a sender name for email. 

Alphanumeric sender IDs must:

  • Be between 3-11 characters 
  • Contain at least one letter
  • Not have any special characters (e.g., ~, &, etc.)

If your brand name matches these criteria, Klaviyo will automatically make your brand name the sender ID. 

If your brand name is too long or fails another criterion, you will be prompted to choose your sender ID. To do so, follow the steps in the next section. 

Edit Your Sender ID

You can edit your alphanumeric sender ID at any time. 

To change your sender ID, navigate to Account > Settings > SMS.

Under Sending Numbers, click the dropdown menu on the right-hand side of the alphanumeric number.

From the dropdown, choose Edit.


In the resulting modal, add your sender ID.

The modal where you can edit or turn off your sender ID

Once you input a sender ID that meets all of the requirements, click Save

The change will take effect immediately and will not affect your SMS deliverability. 

Turn Off Your Alphanumeric Sender ID

Alphanumeric numbers are enabled by default. If you don’t want to send in the UK or Australia, you can turn off the alphanumeric number. Turning off your alphanumeric number means that you will not accidentally send to recipients in these countries, even if you have their consent. 

To turn off your alphanumeric number, head to Account > Settings > SMS and locate your alphanumeric number under the Sending Numbers section. 

On the right side, select the dropdown menu and then click Edit

The Edit button in the actions dropdown for an alphanumeric sender ID

Under Status, click the toggle so that it becomes Inactive

Click Save.

Like with changing the sender ID, turning off the alphanumeric number is effective immediately. 

Since alphanumeric numbers are free, turning off this number does not affect your billing plan. 

Additional Resources

Understanding SMS Sending Numbers

How UK GDPR Affects SMS

About Australia's Anti-Spam Legislation

Was this article helpful?
8 out of 14 found this helpful