Updated October 22, 2026 · App names checked against vendor documentation; vendors rename things, so search the step picker for the key word if a name differs.
This is general information, not legal advice. Texting rules differ by state and change over time. If you run promotions by text or work in a regulated field like healthcare or lending, check your setup with an attorney.
Why a missed-call reply is treated differently
US texting rules mostly come from the Telephone Consumer Protection Act (TCPA) and the FCC rules under it, published in 47 CFR 64.1200. Those rules are aimed at messages people didn't ask for: robocalls, mass promotions, and texts to numbers that were bought or scraped.
A missed-call text back is different in two ways. The customer started the contact by calling you, and the reply is about the reason they called. That's why most lawyers and phone providers treat a single, informational reply as low risk. It isn't a free pass, though. What you say in the text, and what you do with the number afterwards, decide which side of the line you land on.
The checklist: what keeps a missed-call text safe
- It's a reply, not a campaign. One text (or a short back-and-forth the caller continues) about their call. No coupons, specials or "follow us" links in the first message.
- It names your business. "Hi, it's [Business Name]" in the first line. Anonymous texts look like spam to customers and to carrier filters.
- It includes opt-out wording. "Reply STOP to opt out" costs you a few characters and shows you respect the rules.
- STOP actually stops everything. Under the FCC's consent-revocation rule, people can opt out by any reasonable means, including replies like "don't text me", and you must honor it within 10 business days. Make sure your automation checks an opt-out list before sending anything else.
- The number isn't moved into marketing. Adding callers to promo blasts needs separate permission (more on that below).
- Your sending number is registered. If you text from a regular 10-digit US number through Twilio, Quo, RingCentral or similar, your provider will require A2P 10DLC registration.
- You respect quiet hours. The federal rules restrict telemarketing calls before 8am or after 9pm local time, and some states set tighter windows for texts. An informational reply right after a call is usually fine, but don't schedule follow-ups for the middle of the night.
What A2P 10DLC registration is (and why you can't skip it)
A2P 10DLC stands for application-to-person messaging over a 10-digit long code, meaning a normal local phone number used by software. US carriers require businesses that send automated texts from these numbers to register a brand (your business details) and a campaign (what kind of messages you send and how people opt in).
It's a carrier requirement more than a law, but the effect is the same: unregistered traffic gets filtered or blocked, so your missed-call texts may simply never arrive. Registration happens inside your provider's dashboard, usually takes a few days to approve, and has small one-time and monthly fees. When it asks for the campaign description, describe exactly what you do.
[Business Name] sends a one-time automated text reply to customers who call our business number and are not answered. The message identifies our business, asks how we can help, and includes opt-out instructions. Customers opt in by calling us. We do not send marketing messages to these numbers without separate written consent. Reply STOP to opt out, HELP for help.
When it stops being "just a reply"
The biggest risk isn't the missed-call text itself. It's what happens next. These are the common ways a harmless setup drifts into territory that needs explicit written consent:
- Sending weekly specials or seasonal promos to everyone who ever called.
- Following up again and again when the caller never replied (one gentle nudge is reasonable; a drip campaign is marketing).
- Using an autodialer or AI caller to ring back numbers that came in through missed calls.
- Sharing or uploading the numbers to an ads platform or a list vendor.
If you want to market by text, ask for permission in a separate, clear step, for example a checkbox on your booking form that says you'll send offers by text, how often, and how to stop. Keep a record of when and how each person agreed.
Safe scripts you can copy
Hi, it's [Business Name]. Sorry we missed your call, we're with a customer. How can we help? Reply here or book a time: [booking link]. Reply STOP to opt out.
Hi, it's [Business Name]. We're closed right now and will call you back after [time] tomorrow. Reply with what you need and we'll be ready. Reply STOP to opt out.
You're unsubscribed and won't get more texts from [Business Name]. Call us any time at [number].
Yes, text me occasional offers from [Business Name] (up to 2 per month). Msg & data rates may apply. Reply STOP to opt out any time. Consent isn't required to buy.
How to build the opt-out check into your automation
Whatever tool you use, add one step before every send: look up the caller's number in an opt-out list and stop if it's there.
- Zapier: keep a Google Sheet called Opt-outs. Add a Lookup Spreadsheet Row step on the caller's number, then a Filter that only continues when no row is found. A second Zap adds a row whenever an incoming text contains STOP, UNSUBSCRIBE or similar.
- Make: use a Google Sheets Search Rows module followed by a filter on the bundle count.
- n8n: a Google Sheets lookup followed by an IF node; route opt-outs to a no-op.
- Twilio: Twilio handles standard keywords like STOP automatically for many number types, but still keep your own list so your other tools respect it.
The full build, including the voicemail gotcha that stops many setups from ever firing, is in our missed call text back guide. For trade-specific scripts, see the versions for plumbers, HVAC and contractors.
A note for healthcare and other regulated businesses
Dental offices, clinics and therapists have extra privacy rules on top of texting rules. Keep missed-call replies generic (no mention of treatment or appointment types) and use a texting provider that will sign a business associate agreement. Our dental appointment reminder guide covers wording that keeps details out of the message.
Frequently asked questions
Do I need written consent to send a missed call text back?
For a single informational reply to someone who just called your business, most providers and lawyers consider it low risk because the caller started the contact. Written consent becomes important when you send marketing messages. This isn't legal advice; check your state's rules.
Do I have to include "Reply STOP to opt out"?
It's strongly recommended, carriers expect it during 10DLC registration, and it makes opting out easy. Whatever wording you use, every opt-out request has to be honored.
What is A2P 10DLC and do I need it?
It's the US carrier registration for businesses sending automated texts from regular 10-digit numbers. If your missed-call texts go out through Twilio, Quo, RingCentral or a similar provider, you'll almost certainly need it, or your texts may be filtered.
Can I add callers to my promotional text list?
Not without separate, clear permission for marketing texts. Use a distinct opt-in step and keep a record of it.
Is it legal to send the text after business hours?
An immediate reply to a call someone just made is generally treated differently from a scheduled marketing text, but avoid scheduled follow-ups at night and check your state, as some set stricter time windows.
Want this and 11 more automations, step by step?
The Small Business Autopilot pack has 12 automations like this one, each with setup in Zapier, Make and n8n, copy-paste AI prompts, message templates and an honest time-saved estimate.
Get the pack — $19 Free 2-automation sample
Not sure where to start? Try the free automation idea finder: pick your business type and get 5 ideas.