SMS opt-out requirements: STOP, Revocation, and Suppression Lists

What businesses need to do when someone opts out

SMS opt-out requirements are straightforward in principle: when a recipient clearly asks to stop, stop the covered automated texts, preserve the request, and keep the number out of future sends. In practice, the risk sits in the handoff between a reply, customer support, CRM records, audience exports, agencies, and multiple messaging vendors. A working program recognizes standard STOP-style replies, accepts reasonable revocations through other routes, sends at most a tightly limited confirmation, and applies suppression before the next campaign.

This is an operational guide for US commercial messaging teams, not legal advice. Federal rules, state law, the type of message, the sending technology, consent language, and carrier or platform terms can change the answer for a particular program. Have counsel assess your program. For the baseline federal rule covering the specified robocalls and robotexts, the FCC says a recipient may revoke consent at any time and in any reasonable manner. [1][2]

SMS opt-out requirements: legal baseline versus messaging policy

For calls and texts covered by 47 CFR 64.1200(a)(10), a consumer can revoke prior express consent, including prior express written consent, by any reasonable method that clearly communicates a desire to stop further calls or texts. The regulation names reply-text words that are automatically reasonable: STOP, QUIT, END, REVOKE, OPT OUT, CANCEL, and UNSUBSCRIBE. A sender cannot make one channel the exclusive way to revoke. [1]

The list is not a safe harbor for ignoring plain-language requests. A reply outside the named list must be treated as valid when a reasonable person would understand it as asking to revoke consent. The rule also says voicemail or email to a phone number or email address intended to reach the caller creates a rebuttable presumption of revocation when the recipient can produce evidence of the request. [1] A support agent reading “please remove me from texts” should therefore not debate syntax; they should suppress the number and log the route.

The legal rule is different from industry guidance. CTIA's Messaging Principles and Best Practices say senders should allow opt-out at any time, support multiple mechanisms such as call, email, or text, state how to opt out, use standardized STOP wording, and act on normal language such as “please opt me out.” CTIA guidance is not itself a statute or regulation, but wireless providers and messaging platforms can use industry rules and their own policies to review, filter, or suspend traffic. Build to the stricter applicable requirement. [3]

Use STOP instructions—and recognize more than STOP

“Reply STOP to opt out” remains the clearest instruction for a recurring SMS program. It is recognizable, aligns with CTIA guidance, and maps to the FCC's standardized reply list. Do not configure a workflow that only matches an exact, uppercase STOP. Case, punctuation, and ordinary variations should not determine whether a person can leave a list; CTIA specifically advises that de minimis variations should not affect validity. [3]

Keyword handling is necessary but incomplete. Map the FCC's eight listed terms, use normalized matching for surrounding whitespace and punctuation, and maintain a review queue for intent-bearing language that automation cannot classify confidently. Do not use keyword logic to resurrect a subscriber, ask them to complete a form, or make a support ticket a prerequisite to suppression. If a customer later wants messages again, obtain a new affirmative opt-in through a documented flow; see our guide to SMS opt-in requirements.

• Display the program or brand name and a plain opt-out instruction in recurring-program disclosures and message templates.
• Route inbound replies from every sender identity—short code, 10DLC number, toll-free number, and vendor inbox—to the same decision logic.
• Detect the intent before any automated conversational or promotional reply is sent.
• Record the original message, reply text, source number, receiving program, timestamp, action, and any human override.

Confirmation messages: one, prompt, and non-promotional

A confirmation text is permitted, not a new marketing opportunity. Under the FCC rule, a one-time text that merely confirms the revocation does not violate the specified provisions if it contains no marketing or promotional content and is the only additional message after the request. A confirmation sent within five minutes is presumed to be within prior consent; after that, the sender must show the delay was reasonable. [1][4]

Use a terse message such as: “HVSMS Alerts: You’re unsubscribed and will receive no more messages from this program.” Do not add a sale, URL, survey, referral prompt, “text START to rejoin” pitch, or cross-sell. CTIA similarly recommends one final opt-out confirmation per campaign and no further messages afterward. [3]

There is a narrow clarification option where someone has consented to several categories of texts from the same sender. A one-time confirmation may ask whether the revocation covers all categories, but the sender must stop all consent-required texts unless the recipient affirmatively clarifies they want particular messages to continue. Silence is not permission to keep messaging. [1][4] For most retail and lifecycle programs, a broad suppression default is simpler and safer.

Build a suppression list that survives your tech stack

An SMS suppression list is a durable control record, not merely a status field in the campaign tool that received STOP. Its job is to block a number before any automated audience, journey, API send, manual upload, or vendor handoff. The central record should be keyed to a normalized phone number and retain scope information without weakening the default stop rule.

At minimum, retain the number, suppression status, source of the request, raw request or evidence reference, received and processed timestamps, program/sender identity, confirmation status, system that applied it, and a legally reviewed re-opt-in event if one occurs. Keep opt-in evidence adjacent to, not in place of, the opt-out history. A well-designed SMS consent-records audit trail lets your team demonstrate both events without overwriting either.

Apply suppression at two control points: first when an event is ingested, then immediately before dispatch. The second check catches stale audiences, delayed automations, cached segments, and records that arrived through another system. Propagate a STOP from one provider back to the CRM and to every connected sender platform. A nightly sync alone is too slow for a consent-sensitive event.

The FTC's Telemarketing Sales Rule separately requires entity-specific do-not-call lists for covered telemarketing calls and describes seller and telemarketer responsibility for maintaining them. That is not an SMS-specific suppression-list specification, but it reinforces a useful governance lesson: outsourced execution does not remove the business's responsibility to prevent unwanted outreach. [5] Contractually require agencies, CDPs, and messaging vendors to consume current suppression data and return opt-out events.

A practical opt-out workflow for CRM and ecommerce teams

1. Capture the request from replies, inboxes, forms, support calls, email, and any designated opt-out endpoint. Preserve the original evidence before normalization.
2. Classify it. Automatically suppress known STOP-style terms; send uncertain natural-language replies to an exception queue that can suppress on a reasonable-person standard.
3. Write to a central, append-only suppression record and immediately mark the number in every active sending environment. Do not wait for a batch audience refresh.
4. Cancel queued campaigns and journeys, including transactional-looking flows that are actually promotional. Check all sender numbers, brands, and business units according to the applicable legal scope and your counsel-approved policy.
5. Issue no more than one compliant confirmation when your program sends one. Lock the number before the confirmation is dispatched so a concurrent campaign cannot slip through.
6. Reconcile provider events, CRM fields, and send logs; then investigate any post-opt-out send as an incident, not as a routine customer-service ticket.

Build the workflow before pursuing list growth. The same system should reject purchased or ambiguous lists and make consent provenance visible at send time. Pair it with routine SMS list hygiene so old segments and duplicate contact records do not bypass suppression. Your registration and message disclosures also need to accurately describe the program; review your A2P 10DLC registration guide alongside the implementation.

QA tests that expose opt-out failures before customers do

Run these tests after every integration change, new sender identity, vendor migration, or automation launch—and on a scheduled cadence. Test production-like paths with seeded internal numbers rather than assuming a dashboard toggle means the carrier, provider, CRM, and helpdesk are synchronized. Keep the results, timestamps, screenshots, message IDs, and remediation notes as part of the operating record.

• Reply with each listed FCC term, variations such as “stop!”, and plain requests such as “remove me from your marketing texts.” Verify that no subsequent send reaches the test number.
• Opt out through a support email, phone request, and web form. Confirm the request reaches the same central suppression record and meets your internal SLA.
• Place a number in a queued campaign, an abandoned-cart flow, a loyalty journey, and a vendor export; then opt out. Confirm all four are canceled or blocked.
• Inspect the confirmation. It should be one message only, non-promotional, attributable to the correct program, and dispatched promptly.
• Attempt a re-opt-in. Verify that the system requires a new affirmative action and preserves both the prior opt-out and the later opt-in evidence.
• Reconcile the provider's opt-out report with CRM suppression counts and outbound delivery logs. Any mismatch deserves a root-cause review.

Put these checks in the release gate for every campaign and automation. Our SMS campaign checklist can help teams make suppression validation a standard launch control rather than a last-minute compliance review.

The operating standard to adopt now

The commercially sensible standard is simple: every clear opt-out wins immediately, one central suppression record blocks every sender, and evidence remains retrievable. Federal rules establish the floor for covered automated calls and texts; carrier, platform, contractual, state, and program-specific requirements may require more. The teams that avoid avoidable complaints do not treat STOP as a one-way feature. They engineer revocation as a real-time customer preference across the entire messaging estate.

If your program has multiple brands, agencies, inboxes, or lifecycle tools, test the end-to-end path now. HVSMS can map the failure points, define the operating controls, and implement the handoffs—without substituting for legal advice.