10DLC (10-Digit Long Code) is the registration system US carriers require to send business SMS from local 10-digit numbers. Without it, messages can be blocked or filtered.
Why it exists
Carriers want to prevent spam. With 10DLC, the brand and its use cases are registered and vetted, which improves delivery and allows higher volume than an unregistered number.
What you need to comply
- Register the brand (company details).
- Register the campaign or use case (notifications, OTP, support...).
- Send messages with consent and an opt-out.
At TelHarbor we handle the registration and sending from the platform. See Business SMS and sending via API.
Does it apply to Costa Rica?
10DLC applies to messages sent to the United States. For SMS within Costa Rica and other destinations there are different rules, which we also handle.
Brand, campaign and number: how they fit
Registration has three pieces, and the order matters because most rejections come from mixing them up:
- The brand is your company: legal name, tax ID, address and website. Registered once.
- The campaign is what for: account notifications, one-time passcodes, appointment reminders, customer care. A company can have several.
- The number is attached to a campaign. One number should not mix wildly different uses.
What reviewers actually check
Approvers do not only look at company data. They ask for evidence that recipients asked to receive messages:
- How consent is collected: a checkbox on a form, a message the user sends first, a signature on paper. You have to describe it, not just assert it.
- The exact wording users agree to, which must mention frequency, that rates may apply and how to opt out.
- Real sample messages from that campaign.
- A public website whose privacy policy includes the SMS clauses.
That last point catches many people out: if the privacy policy does not explicitly say that mobile opt-in data is not sold or shared, the campaign gets rejected even when everything else is in order.
Throughput limits and how they grow
Registration also sets how many messages per minute you may send. An unregistered number barely delivers at all; a registered campaign starts with a modest limit that grows over time if your traffic behaves: few complaints, few opt-outs, little content reported as spam.
Put differently, reputation is earned. Registering and then blasting a mass campaign on day one does not work.
What gets campaigns rejected
- Describing opt-in vaguely ("customers agree when they sign up") without showing where and with what wording.
- A website with no privacy policy, or one that never mentions SMS.
- Sample messages that do not match the declared use case.
- Mixing marketing with transactional notifications in one campaign.
- Leaving STOP and HELP instructions out of the consent text.
10DLC, toll-free or short code
- 10DLC: local 10-digit numbers. The normal choice for most companies: inexpensive, local identity, enough volume.
- Toll-free: 800/888. Good volume and no 10DLC needed, but it has its own toll-free verification. Handy if you already use the number for calls.
- Short code: 5 or 6 digits. Highest volume and highest cost; justified for large consumer campaigns.
Frequently asked questions
Is it mandatory?
For business SMS to the US, effectively yes: without registration messages are usually blocked.
How long does registration take?
It depends on the case; brand and campaign are approved in days. We manage it.
Do I need 10DLC if I only send verification codes?
Yes. Registration applies to the number and the use case, not to volume. A transactional OTP still has to be registered to deliver reliably.
What happens if I send without registering?
Messages get filtered or blocked with no clear notice, and the number builds a poor reputation, which makes registering later harder.
Can one number serve several campaigns?
Technically yes, but it is a bad idea: mixing very different uses on one number is a common cause of rejection and of poor delivery.
What about sending SMS inside Costa Rica?
10DLC does not apply. Local traffic follows the rules of the carrier and destination country, which we also handle from the platform.