TCPA §227(b) and CTIA SMS Guidelines require SMS to be sent from a registered, stable sender identity — in the US, a 10DLC-registered long code, a carrier-approved short code, or a verified toll-free number. Sending commercial A2P SMS from unregistered long codes is no longer permitted under current US carrier requirements: unregistered traffic is filtered or blocked by AT&T, T-Mobile, and Verizon, meaning messages never arrive. Beyond deliverability, unregistered sending signals non-compliance to carriers, increasing the risk that the number is flagged and all future traffic from the same account is throttled.
Low because the primary consequence is deliverability failure rather than a direct regulatory penalty, but carrier filtering makes unregistered commercial SMS functionally inoperable at scale.
Register your SMS sender identity with carriers before sending commercial A2P traffic. In Twilio Console, navigate to Messaging > Regulatory > A2P 10DLC.
US A2P Registration checklist:
1. Brand registration (one-time): company name, EIN, vertical
2. Campaign registration: use case, sample messages, opt-in description
3. Number association: link your long-code numbers to the approved campaign
Alternatives:
- Toll-Free Verification: faster (1–2 weeks), good for <100k msg/month
- Short Code: 8–12 weeks, highest throughput, best for >1k msg/day
If you use a Twilio messagingServiceSid (pool of numbers), all numbers in the pool must be 10DLC-registered. Verify registration status at Twilio Console > Messaging > Senders.
ID: email-sms-compliance.sender-identity.sms-sender-id
Severity: low
What to look for: Enumerate every relevant item. For SMS compliance, the sender must be identifiable. In the US, this means sending from a registered phone number — a 10-digit long code (10DLC), a short code (5-6 digits, registered with carriers), or a toll-free number (verified with carriers). Sending from random, rotating, or unregistered long codes is no longer permitted for commercial SMS in the US under current carrier requirements. Check the SMS sending configuration: what number or sender ID is used? Is there documentation of 10DLC registration? For international SMS, check whether an alphanumeric Sender ID is used where supported and registered. Look for from or messagingServiceSid in Twilio send calls, or equivalent in other providers.
Pass criteria: At least 1 of the following conditions is met. SMS is sent from a registered, stable sender identity: a verified short code, a 10DLC-registered long code, a verified toll-free number, or a registered alphanumeric Sender ID for international sends. The sender identity is consistent across all messages.
Fail criteria: SMS sent from a pool of random long-code numbers with no 10DLC registration. Sender ID is numeric but changes per message. No evidence of carrier registration.
Skip (N/A) when: The application sends no SMS at all.
Detail on fail: Example: "Twilio configured to send from a standard long code (+12025551234) with no 10DLC registration documentation found. US carriers now require 10DLC registration for commercial A2P SMS.".
Remediation: Register your SMS sender with the relevant carrier programs:
US SMS Sender Registration:
For 10DLC (Application-to-Person long code):
1. In Twilio Console: Messaging > Regulatory > A2P 10DLC
- Register your brand (company info, EIN)
- Register your campaign (use case, message content, opt-in description)
- Associate your long-code number with the campaign
2. Typical approval: 1-5 business days
3. Unregistered 10DLC traffic is filtered by carriers and may be blocked
For Short Codes (highest throughput, most trusted):
1. Apply through Twilio or your provider
2. Carrier application takes 8-12 weeks
3. Best for high-volume marketing campaigns (>1000 msgs/day)
For Toll-Free Numbers:
1. In Twilio Console: Messaging > Regulatory > Toll-Free Verification
2. Faster approval than short codes (typically 1-2 weeks)
3. Good for mid-volume use cases
Using a messagingServiceSid in Twilio (which routes through a pool of registered numbers) is acceptable as long as all numbers in the pool are 10DLC registered.