SMS compliance & 10DLC

Overview

US carriers require businesses sending SMS via standard 10-digit phone numbers to register through the 10DLC (10-Digit Long Code) program. This is a carrier industry requirement, not a Signals-specific rule. Registration ensures your messages are delivered reliably and not filtered as spam.

What is 10DLC?

10DLC is a system that registers your business identity and messaging use case with carriers (AT&T, T-Mobile, Verizon). Once registered:

• Higher deliverability: messages are less likely to be filtered or blocked
• Higher throughput: registered numbers can send more messages per second
• Lower per-message cost: carriers charge lower fees for registered traffic
• Carrier trust: your messages are identified as legitimate business communications

Without registration, outbound SMS may be filtered, delayed, or blocked entirely by carriers.

Registration status

10DLC registration is handled by your account admin. You can check your registration status on the Voice & Channels → Connections page.

Registration involves:

1. Brand registration: your business name, EIN, address, and industry are submitted to The Campaign Registry (TCR)
2. Campaign registration: your messaging use case (customer support, appointment reminders, etc.) is registered
3. Number assignment: your phone number is linked to the approved campaign

Your admin will notify you when registration is complete. The process typically takes 1–5 business days.

Business name prepend

Once registered, Signals automatically prepends your business name to all outbound SMS messages:

Lakeside Dental: Thanks for your inquiry! We'd love to help you schedule an appointment.

This is a compliance best practice: it identifies your business in every message so recipients know who's texting them. The prepend is automatic and cannot be disabled.

The business name comes from Settings → Business Info. Make sure your business name is set correctly before going live with SMS.

Compliance enforcement

Signals runs compliance checks on every outbound SMS before it's sent:

• 10DLC registration validation: confirms your number is registered before allowing sends
• Opt-out handling: the system automatically processes STOP, UNSUBSCRIBE, and similar keywords. Contacts who opt out are flagged and no further SMS is sent to them.
• Content compliance: messages are checked against carrier content policies
• PII scanning: for HIPAA tenants, PII scanning runs before SMS send to prevent Protected Health Information from being transmitted via SMS
• Spam blocklist: manually block numbers that send unwanted messages. Blocked numbers are silently filtered before they enter the pipeline. See Block spam & manage SMS blocklist

All compliance decisions are logged in the audit trail for your records.

What happens if you're not registered

If your number isn't registered for 10DLC:

• Outbound SMS attempts may fail silently or be filtered by carriers
• The system logs the compliance block with a clear reason
• Inbound SMS and voice calls are not affected (only outbound SMS requires registration)

Tips

• Register early. Start the 10DLC registration process as soon as you set up your phone number. Don't wait until you're ready to go live.
• Keep Business Info accurate. The business name in Settings → Business Info is used for both the SMS prepend and 10DLC registration. If it changes, notify your admin.
• Monitor the audit log. If outbound SMS isn't being delivered, check for compliance blocks in the audit trail.
• Opt-out is automatic. You don't need to build rules for STOP keyword handling; Signals manages it for you.