If you’ve spent any time setting up SMS marketing for your business, you’ve almost certainly run into the phrase “A2P 10DLC” and felt the specific kind of exhaustion that comes from reading three different explanations of something and understanding it less than when you started. The terminology is genuinely bad. The concept underneath it, though, is pretty simple and understanding it actually matters if you want your text messages to reach anyone.

So here’s what it is, why it exists, and what you need to do about it.

To understand 10DLC, you have to understand what business texting looked like before it. For years, companies could send automated text messages to customers using regular 10-digit phone numbers; the same kind of number anyone might have. There was no verification, no vetting, no way for carriers to tell a legitimate business sending appointment reminders from a scammer sending fake IRS warnings. And so the scammers ran wild. By the time carriers started paying attention, customers were so conditioned to distrust unexpected texts that even legitimate business messages were getting ignored, filtered, or reported as spam.

The carriers (AT&T, Verizon, T-Mobile) decided to fix this by creating a formal system for distinguishing real businesses from bad actors. That system is 10DLC. The basic logic is: if you want to send automated messages to customers at scale, you have to register your business and tell carriers who you are, what you’re sending, and why. In exchange, your messages get treated as trusted traffic instead of potential spam. The alternative, since August 2023, is that carriers simply block unregistered messages outright.

Breaking it down: “A2P” stands for Application-to-Person. It just means a message sent from business software (a marketing platform, a CRM, an SMS tool) to a real person’s phone. As opposed to Person-to-Person (P2P), which is two humans texting each other. “10DLC” stands for 10-Digit Long Code, which is the technical way of saying a standard local phone number. The kind that looks like (555) 867-5309. As opposed to a short code, which is the 5 or 6 digit number you see on texts from big brands that costs significantly more to set up and operate.

Put it together and A2P 10DLC just means: business software sending messages through a regular-looking local phone number, within a registered and approved framework. That’s it. The jargon is doing a lot of heavy lifting to describe a fairly straightforward concept.

The whole system runs through an organization called The Campaign Registry, or TCR, which was set up by the carriers specifically to manage this. To get registered, you do it in two stages.

First, you register your brand. TCR uses this to verify that you are who you say you are. Brand registration typically takes one to three business days, and there’s a one-time fee involved, usually passed through by whatever SMS platform you’re using.

Second, you register your campaign. In this context, a “campaign” doesn’t mean a specific promotion, it means a category of messaging. You register separately for things like promotional messages, appointment reminders, two-factor authentication codes, customer support conversations, and so on. Each campaign registration requires a description of your use case, examples of the actual messages you’ll be sending, and confirmation that you have proper opt-in consent from the recipients. Campaign approval typically takes two to seven business days. Once approved, your messages are whitelisted and carriers treat them as legitimate, trusted traffic.

One thing worth knowing: you generally don’t navigate TCR directly. Your SMS platform—whether that’s Mobiniti or anyone else—handles the actual submission. You provide the information; they route it through.

This is not one of those compliance things that technically exists but nobody actually enforces. As of December 2024, carriers are blocking all unregistered A2P traffic from 10-digit numbers. Your messages don’t bounce with an error message. They simply don’t arrive. You might not even know it’s happening until you notice your delivery rates have quietly collapsed.

Beyond blocking, there are financial consequences for non-compliance. Unregistered senders face higher per-message fees: $0.012 per SMS and $0.021 per MMS, versus significantly lower rates for registered traffic. And if your messages contain prohibited content categories—the carriers call it SHAFT, which covers sex, hate, alcohol, firearms, and tobacco—fines can reach up to $10,000 per violation. In severe cases, your number or your entire brand can be blacklisted across carrier networks, which is roughly the SMS equivalent of being permanently banned from the post office.

Registration doesn’t give you unlimited license to send whatever you want. Carriers are still evaluating your traffic after approval, and your actual messages need to match the use case you declared. Beyond the SHAFT content restrictions, certain campaign types are outright ineligible for registration. This includes high-risk financial services like payday loans and debt relief, lead generation campaigns that share collected data with third parties, and anything involving deceptive practices.

On the “you need explicit consent” front: this part is non-negotiable. Every person you text has to have opted in. Meaning they actively gave you permission to contact them via SMS. Verbal opt-ins are allowed, but if that’s how you’re collecting consent, you’re required to confirm it in the first message. Your privacy policy and terms of service need to be accessible and clearly explain how you’re using customer data.

If you’ve been doing SMS marketing for a while, you might be used to short codes. Short codes still exist and still work, but they come with significant trade-offs: they start at around $3,000 per month, they only support one-way messaging in most implementations, and they tend to read as obviously promotional to customers in a way that a local-looking number doesn’t.

10DLC numbers look like regular phone numbers, support two-way messaging and voice calls, cost a fraction of what short codes do, and can be set up much faster. For the vast majority of small and mid-sized businesses sending anything from appointment reminders to promotional offers to customer support messages, 10DLC is the practical and financially sensible choice. Short codes make sense at enormous scale or for very specific use cases; 10DLC is the default that works for almost everyone else.

It’s easy to read all of this as a compliance burden: more paperwork, more fees, more things to get wrong. And it is that, a little. But it’s worth remembering what the alternative looked like: an unregulated channel where spam was so rampant that customers stopped trusting text messages from businesses they’d actually opted in with. The whole value proposition of SMS only holds if recipients trust the messages showing up in their inbox. 10DLC is what protects that trust.

Businesses that registered early and built clean, compliant SMS programs are now operating in a channel their competitors are slowly being filtered out of. 

If you’re already registered, the main thing is keeping your campaign descriptions and your actual messages in sync, maintaining clean opt-in records, and staying away from content that will trigger carrier flags. If you’re not registered yet and you’re sending any kind of automated texts to US customers, that’s where to start. And the process, while not exactly fun, is more manageable than the acronym suggests.