A2P 10DLC Explained: Why Business Texts Get Filtered and How Registration Works

If you text customers from a regular 10-digit business number and some messages never arrive — no error, the customer simply says "I never got it" — the cause is usually carrier filtering of unregistered business traffic. This article explains the system behind it: A2P 10DLC.

This explains an industry process plus one federal rule; it isn't legal advice. Registration requirements and fees are set by The Campaign Registry and the carriers, and they change — confirm current details with your messaging provider.

What "A2P 10DLC" means

• A2P (application-to-person) is a business or software texting a person. The opposite, P2P, is one person texting another — what the SMS network was originally built for.
• 10DLC is a standard 10-digit long code: an ordinary-looking phone number, as opposed to a 5–6 digit short code or a toll-free number.

US carriers created the A2P 10DLC system so businesses texting from ordinary numbers declare who they are and what they send. Registration happens in The Campaign Registry (TCR), and carriers use it to decide how much to trust — and how much to throttle — each sender. Unregistered business traffic from 10-digit numbers is exposed to filtering and blocking, so ask your provider whether it will send anything at all before registration is complete.

Toll-free numbers have a separate verification process; registering in TCR doesn't cover them, and vice versa.

Two registrations: brand and campaign

1. Brand. TCR defines the brand as the company the end customer believes is sending the message — your business, with its legal name and tax ID. A brand must be verified before it can register campaigns.
2. Campaign. A description of what you send (customer care, account notifications, marketing, mixed…), with sample messages and how people opt in. Your numbers are then assigned to that campaign.

If a software company or reseller sends on your behalf, TCR's model still treats your business as the brand; the provider registers it for you and appears as a responsible party on the campaign. Be wary of any setup where your messages go out under someone else's brand — carriers evaluate the brand they see.

What carriers expect once you're registered

The CTIA Messaging Principles and Best Practices are the industry's reference. The points that most often cause trouble:

• Consent first. Text people who agreed to hear from you, for the kind of message they agreed to.
• Opt-out must work. Honor STOP — and natural variations such as "stop," "end," "unsubscribe," "cancel," "quit" or "please opt me out." Send one final confirmation and nothing more.
• Disclose the basics in recurring programs: who you are, how to get help, how to opt out, how often you'll text and whether message and data rates may apply.

There's also a federal rule: under the FCC's TCPA regulations (47 CFR § 64.1200(a)(10)), consumers can revoke consent by any reasonable method, words like "stop," "quit," "end," "revoke," "opt out," "cancel" or "unsubscribe" count, and revocations must be honored within 10 business days.

Mistakes that hurt delivery after you register

• Moving numbers between campaigns casually. Each reassignment has to propagate through carrier systems, and delivery can be worse during that window. Plan reassignments, especially around a provider switch.
• Using a campaign for something it didn't declare. Sending promotions on a campaign registered for account notifications is exactly what carrier review looks for.
• Spreading volume across many numbers. CTIA calls this "snowshoeing" — spreading messages over numbers to dodge filters — and treats it as a red flag.
• Ignoring opt-outs or complaints. High opt-out and complaint rates hurt how carriers treat your traffic.

A short checklist before you send

1. Your business's legal name, EIN and address exactly as the IRS has them.
2. A clear description of what you'll send, with 2–3 realistic sample messages.
3. Where and how customers opt in (a web form, a checkbox at checkout, a keyword) — with the consent language visible.
4. A working STOP/HELP flow and a plan for recording opt-outs.
5. Which numbers will send, and whether any are already registered elsewhere.

On SpartanComm

SpartanComm includes two-way SMS and MMS from your business number. If you plan to send reminders, notifications or marketing, talk to us before you start: we'll review your use case and registration status first, instead of finding out from missing messages. Current per-message rates are on the pricing page.