A2P 10DLC, Demystified: A Step-by-Step Guide

Nothing generates more support tickets in a GoHighLevel agency than A2P 10DLC. Not workflows, not funnels, not DNS. A2P — because it is the one part of the platform where the failure is opaque, the feedback is a single unhelpful line of rejection text, and the consequence is that your client's messages simply do not arrive.

The good news is that A2P rejections are boringly repetitive. Once you understand what the carriers are actually checking, the failure modes collapse into about six causes, and every one is fixable in an afternoon.

What is A2P 10DLC, and why did the carriers introduce it?

A2P means Application-to-Person — a message sent by software rather than typed by a human. 10DLC means 10-Digit Long Code, which is the technical term for an ordinary local phone number.

Local numbers were never designed for bulk messaging. They existed for person-to-person texting, and for years businesses quietly used them for automated sending because they were cheap and looked friendly. Carriers tolerated it, then throttled it, then — as spam volumes grew — started filtering it invisibly. You would send 500 messages, see 500 "delivered" receipts from your provider, and none of them would land.

A2P 10DLC is the fix. Rather than guessing which local numbers are legitimate businesses, US carriers now require every business sending automated traffic to register itself and its intent in a central registry — The Campaign Registry, which administers 10DLC registration on behalf of the US carriers. In return, registered traffic gets a sanctioned, throttle-managed delivery path.

The rules governing what you may send, and on what consent, are set out in the CTIA's Messaging Principles and Best Practices — the industry document carriers enforce against. It is not law, but it is the standard your registration is judged by, and it is worth skimming before you register anything.

The mental shift: registration is not paperwork you file to be allowed to send. It is the thing that makes your messages deliverable at all. An unregistered local number sending A2P traffic in the US is not slow. It is blocked.

What is the difference between a Brand and a Campaign?

This is the single most common conceptual confusion, and almost every rejection makes more sense once you have it straight.

A Brand answers "who are you?" It is a legal-identity record — legal business name, EIN or tax ID, entity type, registered address, website, industry vertical, and a contact human. The registry attempts to verify you exist as a real company by matching that submission against authoritative business records, most importantly IRS records for the name/EIN pair.

A Campaign answers "what will you send?" It is a use-case record attached to the Brand. Declared use case (customer care, marketing, mixed, 2FA), a description of what the messages do, several sample messages, and a description of how people opt in and opt out.

They are vetted by different systems for different things. Brand checks are largely automated identity matching. Campaign checks are content and consent checks, often with a human reviewer opening your website to look for a consent checkbox.

Which is why the fix depends entirely on which one failed. A Brand rejection is a records problem. A Campaign rejection is almost always a website problem.

What is a Trust Score, and what actually moves it?

When your Brand is registered, the registry assigns it a Trust Score — a numeric rating, scored 0–100, reflecting how confidently it could verify your business identity (Twilio: Message throughput and Trust Scores for A2P 10DLC). It is not a reputation score. It has nothing to do with how politely you send or how few complaints you generate. It measures how legible your business is to the verification systems, and it sets your volume ceiling:

The exact numbers shift as carriers revise their policies, so treat the ladder as the durable part and confirm current figures in your Trust Center before promising a client anything. What does not shift is the mechanism. Three things move the score:

• Register as a real legal entity, not a sole proprietor. The sole-proprietor path exists for genuinely tiny senders and it is severely capped. If your client has an EIN, use it.
• Be consistent everywhere. Legal name, EIN, address, website. The verification is a string match, not a judgement call. "Acme Marketing, LLC" and "Acme Marketing LLC" can be the difference between a clean match and a failure.
• Pay for external vetting if you land low. Legitimate young companies with a thin public footprint often score badly. You can request third-party vetting, where a specialist provider re-examines the Brand and issues a new score. It costs a modest one-time fee and is usually the fastest path out of a bad tier. There is also an appeal window after scoring — check the current appeal and re-vetting fees with your provider before paying, since they change.

How do you register A2P 10DLC inside GoHighLevel?

The flow lives in the sub-account, under Settings, in the Phone Numbers area — look for the Trust Center or A2P tab. HighLevel documents the screen-by-screen flow in A2P Standard Brand Registration for 10DLC; the order below is what stops you failing it. Do it in this order.

1. Gather the client's real documents first. You need the exact legal business name as filed with the IRS, the EIN, the registered address, the website, and an authorised contact. Do not take the name off their letterhead. Ask for the EIN confirmation letter (Form CP-575) and copy it character for character.
2. Fix the website before you submit anything. This step is out of order in most people's heads, and it is why most people get rejected. A reviewer will open the site. It needs a live privacy policy and visible consent language wherever a phone number is collected.
3. Submit the Business Profile — this creates the Brand. Legal name, EIN, entity type, address, vertical, website. This is the step where a single wrong character costs you a week.
4. Wait for Brand verification. Largely automated, usually quick. If it fails, the culprit is almost always the name/EIN pair.
5. Check the Trust Score before you build the Campaign. If it came back low, decide now whether to pursue external vetting. Finding out after you have promised a client 50,000 sends a day is a bad afternoon.
6. Create the Campaign and declare the use case honestly. Most agency sub-accounts are genuinely "mixed" — appointment reminders plus some promotional content. Declaring "customer care" because it sounds safer, then submitting promotional samples, is a guaranteed rejection.
7. Write sample messages that are literally what you will send. Include the business name in every sample and opt-out language in at least one. If your workflows send links, include a link. Sanitised copy that bears no resemblance to your automation gets caught.
8. Describe opt-in in concrete terms. Not "customers consent." Say where and how — "end users opt in by submitting the contact form at example.com/contact, which contains an unchecked consent checkbox with full disclosure language." If opt-in happens on paper or in person, say so and be ready to provide an image.
9. Link your numbers to the approved Campaign. Numbers not attached to an approved Campaign do not benefit from the registration.
10. Test on a real handset across each major carrier before turning on volume. Provider-side "delivered" is not the same as arrived.

Why do A2P registrations actually get rejected?

Here is the whole list, in roughly the order you will encounter it.

The pattern under all of these is the same. The carriers are not evaluating whether your messages are good. They are evaluating whether a stranger, given only your submission and your website, could confirm that a real business obtained real permission from a real person. Every rejection is that check failing somewhere.

What do throughput and segment limits mean day to day?

Two things constrain you, and they are different.

Throughput is rate. AT&T meters your Campaign in messages per minute; T-Mobile enforces a daily message cap per Brand. Both are tied to your Trust Score. The practical consequence is that a blast to 20,000 contacts does not go out in one burst — it queues and drains at your permitted rate. With a low-tier Brand and a big list, a "send now" campaign can take hours, or hit the daily ceiling and stall until tomorrow.

Segments are how the carriers count. A plain-text SMS holds 160 characters in the standard GSM-7 encoding. Go over that and the message is split, with each part carrying overhead, so a concatenated message gets roughly 153 characters per segment (Twilio: what is the SMS character limit?).

The trap is encoding. Insert a single emoji, a curly apostrophe pasted from Word, or an em dash, and the message silently switches to Unicode — which holds only 70 characters per segment, or about 67 when concatenated. A message you thought was one segment quietly becomes three. You are billed for three, and all three count against your throughput. This is the most common reason an agency's SMS bill is triple what the character count suggested. Strip smart quotes from your templates, and budget for emoji deliberately.

How long does each stage really take?

Be honest with clients here, because the temptation to say "a couple of days" is strong and usually wrong.

• Brand registration — minutes to a few hours, automated.
• Trust Score assignment — immediate on Brand approval.
• External vetting, if needed — typically a few business days.
• Campaign vetting — usually a few business days for a standard use case. Special use cases such as charity, political and franchise take materially longer and often require extra evidence.
• Carrier-side approval after registry approval — varies by carrier, can add days.
• Any rejection-and-resubmit cycle — resets the clock on the failed stage.

End to end, for an agency doing this properly and getting it right on the first or second attempt, one to two weeks is the realistic planning number. Anyone quoting 48 hours is describing the best case and hoping.

What should you check before you submit?

The highest-return habit in the whole process is a pre-flight check. Before any submission, confirm all four:

1. The legal name and EIN are copied verbatim from the client's IRS documentation.
2. The website is live, has a footer-linked privacy policy, and that policy explicitly states SMS consent is not shared with third parties.
3. Every form collecting a phone number has an unchecked consent checkbox with full disclosure language.
4. The declared use case, the sample messages, and what your workflows actually send are the same thing.

Four checks, twenty minutes. They eliminate the overwhelming majority of rejections — a considerably better trade than losing a fortnight and a client's launch date to a missing comma in a company name.

Sources and further reading

Carrier and registry policies change. Before you promise a client a volume or a timeline, confirm the current figures against the primary sources:

• The Campaign Registry — the registry that administers 10DLC Brand and Campaign registration for the US carriers.
• CTIA Messaging Principles and Best Practices — the industry consent and content standard your Campaign is judged against.
• Twilio: Message throughput (MPS) and Trust Scores for A2P 10DLC — how Trust Scores map to per-carrier throughput.
• Twilio: Direct Standard registration guide — the underlying Brand and Campaign registration flow.
• Twilio: what is the SMS character limit? — GSM-7 vs Unicode segment maths.
• HighLevel: A2P Standard Brand Registration for 10DLC — the in-platform steps.