SMS opt-in is the permission a person gives a business to send them text messages, captured in a way you can prove later. For marketing texts, that means clear written consent that names your business and the kind of messages they will get, with an unchecked box or an equivalent action the person takes on purpose.
This guide is for any business that texts leads or customers, from clinics and med spas to insurance agencies, real estate investors, and coaching programs. You will get the three levels of consent, copy-ready language for forms and keywords, the confirmation text to send, the opt-out rules that changed in 2025, and a checklist for your records.
Key takeaways
- Carrier guidelines recognize three levels of consent: conversational (they texted you first), informational (they gave you their number for a purpose), and promotional (marketing, which needs express written consent).
- Good opt-in language names your business, the message types, frequency, "Msg and data rates may apply," and how to opt out (STOP) and get help (HELP).
- The consent box must be unchecked by default and consent cannot be a condition of purchase.
- Send a confirmation text right after opt-in, and keep a record of who agreed, when, where, and to what wording.
- Since April 2025, people can revoke consent by any reasonable means, and requests must be honored within 10 business days. Best practice is immediately.
What is SMS opt-in?
Opt-in is the record that a person agreed to receive texts from you. It matters for two separate reasons:
- The law. The Telephone Consumer Protection Act (TCPA) requires prior express consent for automated texts, and prior express written consent for marketing texts sent with automated systems. Violations carry statutory damages per message, which is why texting class actions are common.
- The carriers. US carriers enforce their own rules through registration and filtering. When you register for A2P 10DLC, reviewers check that your opt-in flow is clear and verifiable, and they reject campaigns that are not.
The three levels of SMS consent
The CTIA Messaging Principles and Best Practices, the industry guidelines carriers follow, describe consent in three tiers:
| Type | Example | Consent needed |
|---|---|---|
| Conversational | A customer texts you a question and you reply | Implied: they started the conversation; your reply should answer it |
| Informational | A patient gives their number when booking and gets reminders | Express consent: they gave you the number for that purpose |
| Promotional | Offers, discounts, new service announcements | Express written consent, captured before you send anything promotional |
The practical rule: consent covers what the person agreed to, and no more. A number collected for appointment reminders is not consent for promotions. A one-time reply to someone who called or texted you (like missed call text back) is not consent to add them to a marketing list.
SMS opt-in language you can copy
Put this next to the phone field on your form, with an unchecked checkbox:
[ ] By checking this box, I agree to receive text messages from [Business Name] about [appointments, offers, and updates] at the number provided, including messages sent by automated technology. Consent is not a condition of purchase. Message frequency varies. Msg and data rates may apply. Reply STOP to opt out or HELP for help. See our [Privacy Policy] and [SMS Terms].
Why each piece is there:
- Business name. Consent is to a specific sender. In January 2025 the Eleventh Circuit vacated the FCC's "one-to-one" consent rule before it took effect, but naming your business clearly is still the standard.
- Message types. Reviewers and courts look at what the person agreed to receive.
- Automated technology. This is what makes it written consent for automated marketing texts.
- Not a condition of purchase. Required for marketing consent.
- Frequency, rates, STOP, HELP. Carrier reviewers expect all four. Twilio's rejection guidance also requires links to a privacy policy and terms.
- Unchecked box. A pre-checked box is not active consent, and Twilio lists "opt-in must be unchecked by default" as its own rejection reason.
If you only send appointment reminders and service messages, narrow the language to those, and keep promotional consent as a separate, optional box.
Other ways to collect opt-in
Keyword opt-in. "Text JOIN to (555) 123-4567 for updates." Show the terms where the keyword is advertised, then send a confirmation that repeats them.
Verbal opt-in. A front desk script: "Can we text you appointment reminders at this number? You can reply STOP anytime." Log who agreed, when, and who asked. Verbal consent works for informational texts; get written consent for marketing.
Paper or in-person forms. Same language as the web form. Keep the signed form or a scan.
QR codes. Point to a web page with the same form and disclosures, not straight to a text thread with no terms.
Whatever the method, carrier reviewers want to be able to see it. If your form sits behind a login or happens offline, host screenshots or a photo of the form on a public page.
The confirmation text to send
Send one right after someone opts in. It confirms the subscription and gives them an easy exit:
[Business Name]: Thanks for signing up for appointment and offer texts. Msg frequency varies. Msg and data rates may apply. Reply HELP for help, STOP to opt out.
Carrier guidelines expect a confirmation for recurring programs, and it protects you: if someone did not mean to sign up, they stop right away instead of complaining later.
Opt-out rules: what changed in 2025
The FCC updated its revocation rules, and most of the changes took effect on April 11, 2025 (Carlton Fields summary):
- People can revoke consent by any reasonable means. Replies like STOP, QUIT, END, REVOKE, OPT OUT, CANCEL, and UNSUBSCRIBE are treated as valid revocations. So is "please stop texting me."
- You must honor revocation within 10 business days. Most platforms stop instantly, which is what you want.
- You may send one confirmation that the person opted out, as long as it contains no marketing.
A related "revoke-all" requirement, which would make one opt-out apply across a business's different message programs, was delayed by an FCC waiver. Watch for updates if you run several texting programs.
Records to keep
If a consent dispute ever comes up, these are what protect you:
- The phone number and name
- Date and time of consent
- Where it happened (form URL, keyword, location, staff member)
- The exact consent wording shown at that moment (version your language)
- IP address or device info for web forms, where available
- The confirmation text and any later opt-out, with dates
Most CRMs can store this automatically on the contact record. We set it up as a standard part of the follow-up and sales systems we build, because a lead you cannot legally text is a lead you cannot follow up with.
Common opt-in mistakes
- Pre-checked boxes or consent buried in general terms of service
- One consent covering "partners" or other companies
- Using reminder consent for promotions
- Buying lists or importing contacts who never opted in
- Texting before the confirmation, or with no STOP instructions
- Regulated products without age gating (see our guide to SHAFT texting rules)
- Clinics including health details in texts (see HIPAA compliant text messaging)
This is general information, not legal advice. If you buy leads, text at high volume, or operate in several states with their own texting laws, have counsel review your consent flow.
Frequently asked questions
What is SMS opt-in?
SMS opt-in is the permission a person gives a business to send them text messages. For marketing texts it should be clear written consent that names the business, describes the messages, and tells people how to opt out.
What should SMS opt-in language include?
Your business name, the types of messages, that messages may be automated, that consent is not a condition of purchase, message frequency, "Msg and data rates may apply," STOP and HELP instructions, and links to your privacy policy and SMS terms.
Does the opt-in checkbox have to be unchecked?
Yes. Consent must be an active choice. Pre-checked boxes are not treated as valid consent and are a common reason carriers reject texting registrations.
Can I text someone who gave me their number but did not check the box?
You can usually send informational or service messages tied to the reason they gave you the number, such as appointment details. Do not send marketing texts without express written consent.
How fast do I have to honor an opt-out?
Under FCC rules in effect since April 2025, within 10 business days, and opt-outs can come in any reasonable form. Best practice is to stop immediately and send at most one non-marketing confirmation.
If you want consent captured, stored on every contact, and enforced automatically by your CRM, book a call.