A2P 10DLC: why your business texts do not arrive, and what registering actually promises.

You set up appointment reminders, sent a test to your own phone, and it arrived. Then you turned it on for real and the messages started disappearing: no bounce, no error anyone can find, just customers saying they never got anything.

This is usually registration. And the part worth understanding is not how to fill in the form, which takes an afternoon, but what you are signing up to when you do.

What the carriers actually built

A2P stands for application-to-person: any message your software sends rather than one you thumb out yourself. 10DLC is the ordinary ten-digit number it goes out from. Twilio describes the standard as one US carriers put in place to ensure that SMS traffic to US end users through long code numbers is verified and consensual.

Registration has two halves. A brand establishes who is sending, and for standard brands that means a real tax ID. A campaign describes what you are sending, and specifically how people opt in, how they opt out, and how they get help.

Read that second half again, because it is a description of a process, and somebody is going to assume you are running it.

Registration is a delivery problem. Consent is a legal one.

These get merged constantly, including by the people selling the setup, and they are not the same thing at all. (Email has its own version of this split, with different acronyms and the same underlying question.) Registration decides whether carriers let your traffic through: unregistered A2P traffic picks up additional carrier fees, and delivery becomes something you hope for rather than something you rely on. That is the problem you noticed when the reminders stopped arriving, and filing genuinely does fix it.

Consent decides whether you were allowed to send the message in the first place. Nothing in an approved registration makes your contact list lawful. You can be fully registered and thoroughly in the wrong, and the approval email will not mention it.

The promise on the form

Twilio's messaging policy states that you must obtain prior express consent from the recipient in accordance with all applicable laws. Recipients are supposed to know who is contacting them and how their number will be used, and consent is meant to be given for the specific kind of message you plan to send.

Then the sentence that catches people. The policy requires you to retain proof of all consents for as long as your legal obligations demand, and to provide proof of a recipient's consent on written request.

Proof. Not a recollection that they were a customer.

This is where most small businesses are genuinely exposed, and it has nothing to do with intent. The campaign registration describes a web form with a consent checkbox. The actual numbers came off paper intake sheets with no SMS line on them, or out of a spreadsheet somebody inherited, or from the front desk typing them in while a customer was still on the phone. None of that produces a record you could hand over. The gap is rarely deliberate; it is just that the form was filled in by whoever was setting up the software, describing the process as it ought to work, while the business carried on collecting numbers the way it always had. Nobody connected the two, because nothing forces you to until somebody asks.

Being an existing customer is not the same as having agreed to be texted, and the fact that they gave you the number for a quote does not carry over to a marketing broadcast about a spring promotion. If you are wiring up review request texts or reminder sequences, the question to settle first is where each number came from and what the person was told at the time.

STOP is stricter than most automations are built for

Your first message has to tell people how to get out, using "Reply STOP to unsubscribe" or a standard equivalent. The recognised keywords go well beyond STOP alone: STOPALL, UNSUBSCRIBE, OPTOUT, CANCEL, END, REVOKE and QUIT all count.

When someone revokes consent you may send one final message confirming it, and after that any further messages are prohibited. One. Not one per automation.

That is the detail that trips up businesses running several sequences at once, because a person who texts STOP has usually opted out of a system, not a campaign, and platforms differ in how thoroughly they propagate that. Test it deliberately. Opt a spare phone out, then trigger every automation you run — the reminder, the review request, the follow-up — and confirm all of them stay silent. It is a twenty-minute test that tells you something no dashboard will.

What getting it wrong costs

Carrier penalties are published and unsentimental. T-Mobile charges $1,000 for program evasion, the practice of spreading traffic across numbers to dodge filtering, and $10,000 per violation for prohibited content. Certain categories are off the table entirely, including gambling, debt collection, and the family of get-rich-quick offers.

The TCPA exposure sitting behind all of this is a separate matter, it is real, and it is a question for a lawyer rather than for an agency blog. Nothing here is legal advice. If you are texting at any volume and cannot produce consent records, that conversation is worth having before the next campaign rather than after it.

Before you file

Get the tax ID details in front of you and use the exact legal entity name rather than the trading name on your sign, since the brand is an identity check and identity checks are unforgiving about punctuation.

More importantly, build the opt-in you are about to describe. Put the checkbox on the form with wording that says what people will receive, add an SMS line to the paper intake sheet, and make sure whatever the receptionist uses records the moment somebody said yes. Then register a campaign that matches what you built, because the alternative is describing a process you would have to invent under pressure.

If your texting sits inside GoHighLevel or a similar platform and you are not sure whether your sequences honour an opt-out across the board, book a strategy call. Checking it is quick, and it is a much better week to find out than the one where somebody asks you for proof.