ABOUT THIS ENTRY
Category Core: Compliance
Reading time: 1 min
Updated: Sep 2026
A2P Messaging
Definition
A2P messaging (application-to-person messaging) is any text a business sends from software instead of a staff member's own phone, such as an appointment reminder, a recall notice, or a payment link.
Why the distinction matters
Carriers treat A2P texts differently from person-to-person (P2P) texts because bulk automated traffic looks like spam unless the sender is known. US carriers require A2P senders to follow rules set by CTIA, the wireless industry group. For regular 10-digit numbers, that means registering a brand and a campaign with The Campaign Registry.
For a practice, delivery is at stake. Texts from unregistered senders, or texts that drift from the registered use case, may be filtered or blocked.
Example
A practice registers its number for appointment reminders, then starts sending flu clinic promos from it. Some texts stop arriving, and the front desk notices only when unconfirmed slots pile up. Updating the campaign before the first promo was the fix.
Frequently Asked
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Why do appointment reminder texts count as A2P messaging?
They're sent by software, on a schedule, to many patients at once. That's the pattern A2P rules cover, even when staff uses the same tool and number to reply to patients one by one.
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How does A2P registration affect whether patients get our texts?
Registration tells carriers who is sending and what kind of messages to expect. Texts from unregistered numbers, or that don't match the registered use case, may be filtered or blocked.
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Why do texts from practice software count as A2P when texts from a staff phone don't?
A staff phone sends one-to-one texts, which carriers treat as person-to-person (P2P). Practice software sends automated texts to many patients from one number, so carriers count it as A2P and require the sender to register.