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    US · +1 · MCC 310–316

    United States SMS guide

    What actually changes when you send OTP, transactional or marketing SMS into the United States — separated into federal law and regulation, carrier and industry-programme policy, and what we recommend operationally.

    Last reviewed: 1 August 2026 · North America

    On this page

    At a glance

    A quick operational read on the United States. Registration and verification requirements come from the carrier and industry-programme layer, not from federal statute — and anything marked route-dependent is confirmed for the specific path your traffic uses.

    SMS to mobile
    Carrier or route policy
    Supported
    Number format
    Law / regulation
    +1 NPA NXX XXXX — ten national digits after +1
    NANP validation
    Flowstates recommendation
    +1 is shared across the North American Numbering Plan; confirm the destination is actually US and mobile-capable before routing
    Alphanumeric senderID
    Carrier or route policy
    Not supported on standard US SMS routes
    Registered A2P 10DLC
    Carrier or route policy
    Supported; brand and campaign registration is required for application-originated US-bound SMS/MMS over a +1 ten-digit long code, and unregistered traffic is blocked on current major routes
    Verified toll-free
    Carrier or route policy
    Supported; full messaging verification is required on current US and Canada A2P toll-free paths rather than as a universal rule across every provider, and major provider routes block unverified or still-pending toll-free traffic
    Dedicated shortcode
    Carrier or route policy
    Supported through selected programmes; US shortcodes are normally five or six digits
    International long code
    Carrier or route policy
    Not supported as a standard US A2P sender
    Two-way SMS
    Carrier or route policy
    Supported when the selected 10DLC, toll-free or shortcode service is configured for inbound messaging
    Number portability
    Law / regulation
    Available — the original range does not identify the current carrier
    Reassigned Numbers Database
    Law / regulation
    Routine use is not mandatory; it can support the federal safe-harbour framework when the regulatory conditions are met
    Reassignment controls
    Flowstates recommendation
    Use the Reassigned Numbers Database or equivalent controls for recurring programmes, dormant lists and older consent records
    Concatenation
    Carrier or route policy
    Generally supported on major routes; test the exact sender and carrier path
    MMS
    Carrier or route policy
    Supported on eligible 10DLC, toll-free and shortcode routes where enabled
    Landlines
    Carrier or route policy
    Not a dependable SMS destination; any text-to-speech conversion is provider and carrier route behaviour
    Marketing
    Law / regulation
    TCPA, federal and company-specific Do Not Call duties, applicable state law, consent and revocation controls apply
    Revocation
    Law / regulation
    Reasonable covered revocation requests must be honoured within a reasonable time not exceeding ten business days where 47 CFR 64.1200 applies
    Suppression standard
    Flowstates recommendation
    Immediate cross-system suppression is the Flowstates standard rather than the ten-business-day maximum
    Cross-programme revocation
    Law / regulation
    The FCC requirement to treat an opt-out from one informational message as covering unrelated messaging is waived until 31 January 2027; verify the current FCC record before relying on that date
    Last reviewed
    Flowstates recommendation
    1 August 2026

    Route-dependent: “Route-dependent” means the behaviour is decided by the carrier, provider and industry programme your traffic uses, not by US statute. Two providers can behave differently on the same day, and a programme can change its policy. Confirm before launch.

    Law, route policy and recommendation

    The United States is the market where these three layers are most often confused. Registration is not consent, and consent is not registration. Every statement on this page is labelled so the right team can act on it.

    • Law / regulation

      Law and regulation

      Federal obligations: the Telephone Consumer Protection Act and the FCC's implementing rule at 47 CFR 64.1200, plus FTC telemarketing rules where they apply. These bind you whichever provider or carrier you use. State telemarketing and mini-TCPA laws can be stricter, and this guide is not a 50-state legal survey.

    • Carrier or route policy

      Carrier or route policy

      A2P 10DLC brand and campaign registration through The Campaign Registry, toll-free messaging verification, shortcode programme requirements, CTIA messaging principles, carrier filtering, throughput and use-case acceptance. This is industry and carrier governance, not federal law — and it changes independently of the statute.

    • Flowstates recommendation

      Flowstates operational recommendation

      What we ask customers to do because it protects deliverability and keeps you comfortably inside both the law and route policy. Deliberately stricter than the legal or programme minimum.

    Numbering and networks

    The basics your validation layer and templates need to get right before the first send.

    • Law / regulationNumbering plan

      The United States participates in the North American Numbering Plan and uses country code +1. National numbers carry ten digits: a three-digit Numbering Plan Area (NPA) code followed by a seven-digit local number.

    • Flowstates recommendation+1 is shared

      Country code +1 is shared with Canada and multiple Caribbean and other NANP territories. A syntactically valid +1 number is not automatically a United States destination — validate the country or territory before routing, or you will send US-registered traffic to a country it was never approved for.

    • Law / regulationLine type is not in the prefix

      Mobile and fixed numbers share the same ten-digit syntax. Do not infer line type from the area code or the prefix; the format tells you nothing about whether the destination can receive SMS.

    • Law / regulationNumber portability

      Number portability is available, so the original number range does not reliably identify the current carrier.

    • Law / regulationMobile country codes

      The United States has ITU mobile country codes 310 through 316. Abbreviated provider tables that show only 310 or 311 do not represent the whole allocation.

    • Carrier or route policyCarrier paths to test

      The primary paths to test operationally are AT&T, T-Mobile and Verizon, plus MVNO destinations that ride those host networks. We do not publish market shares, and not every supplier holds direct coverage on every path.

    • Flowstates recommendationValidation before sending

      Run line-type, country or territory and current-carrier lookup before sending. Resolve at send time rather than caching a carrier against a contact record.

    • Carrier or route policyLandlines

      Standard business SMS should target mobile-capable destinations. Some provider paths may attempt landline delivery and some carriers may convert it to text-to-speech, but that is not a normal SMS experience and must not be relied upon.

    E.164 example

    +1 212 555 01XX

    A deliberately fictional 555 example: country code 1, then the three-digit area code, then the seven-digit local number. Store the full ten national digits and confirm the number is a US, mobile-capable destination rather than another NANP territory.

    Sender options

    The United States has no alphanumeric sender option on standard routes. Every compliant application-originated programme runs on a registered ten-digit long code, a verified toll-free number or an approved shortcode — and each of those is an industry-programme requirement rather than a legal one.

    Carrier or route policy

    This whole comparison — best for, what the recipient sees and replies — describes carrier and provider route behaviour and industry programme requirements on current US paths, not United States statute. It varies by supplier, programme and carrier, and is confirmed before launch rather than guaranteed universally.

    Registered A2P 10DLC number

    Best for
    Local conversational, OTP, transactional and permissioned marketing programmes at normal business scale
    What the recipient sees
    The registered US ten-digit local number assigned to the service
    Replies
    Available when inbound SMS is configured

    Verified toll-free number

    Best for
    National service, support, OTP, transactional and permissioned marketing programmes using a recognisable toll-free identity
    What the recipient sees
    The verified US toll-free number assigned to the programme
    Replies
    Available when inbound SMS is configured

    Dedicated short code

    Best for
    Selected high-scale and time-sensitive programmes requiring a consistent five- or six-digit identity
    What the recipient sees
    The programme's dedicated short code
    Replies
    Route- and programme-dependent; commonly supported where configured

    Alphanumeric or unsupported international sender

    Best for
    Not a production US SMS option
    What the recipient sees
    Traffic may be rejected, filtered or presented through a different supported numeric path depending on provider
    Replies
    No reliable reply path

    Route policy: on current US paths alphanumeric senderIDs are not a supported originating identity, unregistered application-originated traffic over +1 ten-digit local numbers is blocked by the carrier ecosystem, unverified toll-free messaging is blocked or heavily filtered, and short codes are only available through the applicable programme. Treat all of that as carrier and provider policy rather than statute; Flowstates confirms the live path privately. Flowstates recommendation: put a recognisable brand and the message purpose in the body, and do not rely on replies unless inbound messaging is configured and tested.

    What changes by traffic type

    The United States is not one rulebook. The same destination behaves very differently depending on the category you send, the sender type you registered and the consent you hold.

    OTP / authentication

    Suitable on a registered or verified high-quality sender path.

    • Carrier or route policy

      Run OTP on a registered 10DLC, verified toll-free or approved shortcode path. There is no valid unregistered alternative on current major routes.

    • Flowstates recommendation

      A user-requested OTP supports that specific authentication exchange. Do not treat it as permission for unrelated marketing.

    • Flowstates recommendation

      Keep copy purely transactional, concise and within one segment where practical.

    • Flowstates recommendation

      Identify the brand, state what the code is for and include an appropriate expiry cue.

    • Flowstates recommendation

      No promotional copy in authentication templates.

    • Flowstates recommendation

      Use branded domains if a link is genuinely necessary.

    • Flowstates recommendation

      Monitor delivery, latency, completed-verification conversion and carrier and sender performance rather than submitted-versus-delivered counts alone.

    • Flowstates recommendation

      Configure carrier-grade failover, but never fail over to an unregistered or unverified sender. Every fallback sender must itself be valid for the traffic.

    • Carrier or route policy

      Replies only where configured. Do not require a reply for authentication unless the service was designed and tested for it.

    Transactional / service

    Suitable for alerts, confirmations, reminders, account updates and support on a valid registered or verified sender.

    • Flowstates recommendation

      Consent and expectations must cover the service purpose. Do not turn a service opt-in into marketing permission.

    • Flowstates recommendation

      Identify the brand and the purpose of the message.

    • Flowstates recommendation

      Keep marketing copy out of transactional templates.

    • Flowstates recommendation

      Use branded domains for links rather than a public or shared shortener.

    • Carrier or route policy

      Keep materially different use cases separated where campaign or sender policy requires it.

    • Carrier or route policy

      Support HELP and programme keyword handling appropriate to the registered or verified sender programme.

    • Law / regulation

      Monitor and honour every reasonable revocation method. Programme keywords are not the exclusive method a recipient may use.

    • Flowstates recommendation

      Test MMS, Unicode and concatenation on the exact sender and carrier path before launch.

    Marketing / promotional

    Federal consent and Do Not Call duties apply, state law can be stricter, and registration never substitutes for permission.

    • Law / regulation

      47 CFR 64.1200 requires prior express written consent for covered autodialed, artificial or prerecorded telemarketing calls or texts to wireless numbers, subject to the rule's scope and exceptions. This is not a universal statement that every marketing text under every technology and factual scenario always requires written consent.

    • Flowstates recommendation

      Flowstates launch standard is nevertheless prior express written, seller-specific, purpose-specific and SMS-channel-specific permission for every promotional SMS programme, unless qualified US counsel documents another lawful approach and the selected route accepts it.

    • Law / regulation

      A valid written agreement must clearly authorise the seller and the telephone number, provide a clear and conspicuous disclosure, and state that consent is not a condition of purchasing. Electronic signatures can qualify.

    • Law / regulation

      The FCC's 2023 one-to-one consent amendment is not current federal law: the Eleventh Circuit vacated it in Insurance Marketing Coalition Ltd. v. FCC on 24 January 2025, before it took effect. Do not design a programme around it and do not treat it as a live requirement.

    • Flowstates recommendation

      Flowstates standard regardless of the vacatur: permission must be clearly attributable to one identified seller or brand, one purpose and the SMS channel, with the disclosure version retained as evidence.

    • Carrier or route policy

      10DLC registration, toll-free verification or shortcode approval never substitutes for consent, and is not proof of legal compliance.

    • Law / regulation

      Federal National Do Not Call and company-specific Do Not Call requirements can apply to telemarketing texts to wireless numbers. Where applicable, use a National DNC data version no older than 31 days and retain the evidence.

    • Law / regulation

      Maintain a company-specific suppression list. Applicable requests must be honoured within no more than ten business days under the rule, and company-specific Do Not Call requests must be retained for five years.

    • Flowstates recommendation

      Flowstates suppresses immediately rather than using the ten-business-day maximum as an operating target.

    • Law / regulation

      State telemarketing, mini-TCPA, quiet-hour, registration and Do Not Call laws may be stricter than the federal rules. This guide is not a 50-state legal survey.

    • Flowstates recommendation

      Flowstates recommendation: validate the recipient-state rule with qualified US counsel before a marketing launch.

    • Law / regulation

      The federal 08:00–21:00 local rule applies to “telephone solicitations” as defined in the rule. Because prior invitation or permission, an established business relationship and nonprofit messages are excluded from that definition, 08:00–21:00 is not a universal statutory window for every consented promotional SMS.

    • Flowstates recommendation

      Flowstates conservative campaign window: 09:00–20:00 recipient local time, with any stricter state or carrier rule taking precedence. This is a recommendation, not a statutory window.

    • Flowstates recommendation

      Do not use purchased lists.

    • Carrier or route policy

      Keep the registration and campaign description, opt-in wording, sample copy, sender and live content materially aligned.

    • Flowstates recommendation

      Use a branded domain. Do not use public or shared shorteners, URL cycling or redirects intended to evade filtering.

    • Carrier or route policy

      Category acceptance stays route-specific and is confirmed privately rather than published as a list.

    Operational compliance checklist

    What we expect to see in place before a United States route goes live.

    • Flowstates recommendation

      Store US destinations as +1 plus ten national digits.

    • Flowstates recommendation

      Validate that the +1 number belongs to the United States rather than another NANP territory.

    • Flowstates recommendation

      Validate line type, mobile capability and current carrier; never infer them from the area code or prefix.

    • Carrier or route policy

      Select one of the valid sender paths: registered 10DLC, verified toll-free or approved shortcode.

    • Carrier or route policy

      Confirm registration or verification is fully approved before sending. Pending is not live.

    • Carrier or route policy

      Keep the legal entity, brand name, website, use case, opt-in journey, sender, sample copy and live traffic consistent.

    • Flowstates recommendation

      Separate OTP, transactional or support and marketing purposes, and keep their consent records separate.

    • Flowstates recommendation

      Retain the number, timestamp, source, disclosure wording and version, seller or brand, purpose, channel and evidence of the consent action. This exact record set is the Flowstates evidence standard rather than a prescribed federal format.

    • Carrier or route policy

      For recurring programmes, ensure the confirmation or disclosure contains the programme identity, expected frequency or recurrence, message and data-rate disclosure where programme policy uses it, HELP and STOP information and privacy and terms links appropriate to the route. These are CTIA and carrier practices rather than federal statute.

    • Flowstates recommendation

      Identify the brand and the purpose in every message.

    • Flowstates recommendation

      Monitor replies plus the designated web, phone and email revocation routes, so no reasonable request is missed.

    • Law / regulation

      Recognise STOP, QUIT, END, REVOKE, OPT OUT, CANCEL, UNSUBSCRIBE and natural-language equivalents.

    • Flowstates recommendation

      Suppress immediately across every sending system and send no more than one non-marketing confirmation.

    • Law / regulation

      Maintain National Do Not Call screening where applicable using data no older than 31 days, plus a company-specific five-year suppression record.

    • Flowstates recommendation

      Review recipient-state requirements with qualified US counsel before a marketing launch.

    • Flowstates recommendation

      Use 09:00–20:00 recipient local time as the Flowstates default; stricter law or carrier policy wins.

    • Flowstates recommendation

      Run Reassigned Numbers Database or equivalent reassignment controls for stale consent and recurring programmes.

    • Flowstates recommendation

      Do not use purchased lists, number cycling, snowshoeing, shared sender identities, public shorteners or filter-evasion techniques.

    • Flowstates recommendation

      Use a branded short domain.

    • Carrier or route policy

      Test AT&T, T-Mobile, Verizon and representative MVNO-hosted paths.

    • Carrier or route policy

      Test SMS and MMS, Unicode, concatenation, inbound replies, HELP and opt-out handling.

    • Flowstates recommendation

      Keep template, registration and verification, consent, Do Not Call, reassignment, opt-out, suppression, campaign and route-approval records.

    Encoding and delivery

    US English copy normally fits GSM-7, but a single pasted character can change the encoding and the segment count, and delivery behaviour still depends on the sender type and carrier path you actually bought.

    GSM-7, single segment
    160 characters
    GSM-7, concatenated
    153 characters per segment
    Unicode / UCS-2, single segment
    70 characters
    Unicode / UCS-2, concatenated
    67 characters per segment
    • Flowstates recommendation

      Smart punctuation, emoji and formatting pasted from a document can switch the encoding to Unicode, which shortens the segment and changes the segment count. Check the encoding your template actually produces.

    • Carrier or route policy

      Concatenation and MMS are generally supported on major US routes, but behaviour remains sender-, provider- and carrier-specific.

    • Flowstates recommendation

      A provider's maximum character length is a technical ceiling, not a design target. Write concise templates instead of sizing copy to the provider limit.

    • Flowstates recommendation

      Keep OTP to one segment where practical, and test the final English copy, Unicode symbols, links and MMS on the exact 10DLC, toll-free or shortcode route.

    • Carrier or route policy

      Treat provider-specific character-substitution warnings as route policy for that provider. Do not turn one supplier's note about a single symbol into a universal US claim.

    • Flowstates recommendation

      Validate mobile capability before sending. Landline delivery and any text-to-speech conversion are not a dependable SMS experience.

    A country guide is only useful when the route follows it.

    Knowing the US rules is the easy half. Keeping every send inside them — on registered senders, across carrier policy that changes independently of the law — is the operational half, and that is the part we run.

    • Per-country and per-category routing

      OTP, transactional and marketing traffic take different US paths, with the right sender type and policy applied to each category.

    • SenderID management

      We manage sender identity across registered 10DLC, verified toll-free and shortcode programmes, and keep the registered use case aligned with what you actually send.

    • Carrier-grade failover

      When a US path degrades, traffic moves to another valid registered or verified sender — never to an unregistered one.

    • Per-route visibility

      Delivery, latency and OTP conversion measured per sender and per carrier path, so a filtering change shows up as data rather than as complaints.

    • 24/7 vendor escalation

      We chase the supplier and the carrier. You get the update, not the ticket queue.

    • BYOV / BYOG

      Keep your existing US supplier, numbers and contracts and let us operate the routing, or use ours.

    • Branded short links

      Links on your own domain instead of a shared shortener, which US carrier filters treat very differently.

    Developer docsBranded short links

    What we need to validate your United States route

    Send us these and we will come back with the sender options, the registration or verification path that applies and the policy that governs your category.

    • Company or legal entity, business identity and website
    • Customer-facing brand name
    • Traffic category and use case
    • English sample templates for each distinct use case
    • Expected monthly volume and peak sending rate
    • Preferred sender: 10DLC, toll-free or shortcode
    • Existing US sender inventory and current provider or vendor
    • Opt-in journey, screenshots or evidence and the exact disclosure wording
    • Privacy-policy and terms URLs
    • Whether marketing is included, the recipient states and the Do Not Call and state-law review owner
    • Internal opt-out and suppression process and owner
    • Reassigned-number or RND process for recurring or older consent records
    • Link domains you intend to use
    • Whether you need inbound replies, HELP handling or MMS
    • Whether any message exceeds one segment
    • Target launch date
    Validate my United States routeBook a messaging review

    Frequently asked questions about SMS in United States

    Can I send SMS to mobile numbers in United States?

    A quick operational read on the United States. Registration and verification requirements come from the carrier and industry-programme layer, not from federal statute — and anything marked route-dependent is confirmed for the specific path your traffic uses. SMS to mobile: Supported. Number format: +1 NPA NXX XXXX — ten national digits after +1. NANP validation: +1 is shared across the North American Numbering Plan; confirm the destination is actually US and mobile-capable before routing. Alphanumeric senderID: Not supported on standard US SMS routes.

    Which sender ID options work for SMS in United States?

    The United States has no alphanumeric sender option on standard routes. Registered A2P 10DLC number — Best for: Local conversational, OTP, transactional and permissioned marketing programmes at normal business scale. Verified toll-free number — Best for: National service, support, OTP, transactional and permissioned marketing programmes using a recognisable toll-free identity. Dedicated short code — Best for: Selected high-scale and time-sensitive programmes requiring a consistent five- or six-digit identity. Alphanumeric or unsupported international sender — Best for: Not a production US SMS option.

    What are the consent and opt-out requirements for SMS in United States?

    US messaging compliance is two separate systems that are constantly confused. The Telephone Consumer Protection Act and the FCC's implementing rule at 47 CFR 64.1200 are federal law and regulation, and they apply to text messages to wireless numbers to the extent the rule states. CTIA Messaging Principles and Best Practices, The Campaign Registry, toll-free verification and shortcode programme monitoring are industry and carrier governance. They are not statute, and compliance with them is not compliance with the TCPA. Under 47 CFR 64.1200, prior express written consent has defined elements: a written agreement bearing a qualifying signature, clear authorisation by the seller, the destination telephone number, clear and conspicuous disclosures, and no requirement that consent be a condition of purchase.

    How many characters fit in an SMS to United States?

    US English copy normally fits GSM-7, but a single pasted character can change the encoding and the segment count, and delivery behaviour still depends on the sender type and carrier path you actually bought. GSM-7, single segment: 160 characters. GSM-7, concatenated: 153 characters per segment. Unicode / UCS-2, single segment: 70 characters. Unicode / UCS-2, concatenated: 67 characters per segment.

    Sources and change control

    Regulator, statute and industry references behind this guide. eCFR, FCC and FTC material controls the federal legal wording; NANPA and ITU control numbering and mobile country codes; CTIA, The Campaign Registry and the US Short Code Registry describe industry governance rather than statute; and Twilio sources describe that provider's current route behaviour only.

    Change log

    • 1 August 2026 — Initial publication; separated TCPA and Do Not Call obligations from CTIA/carrier registration policy and compared registered 10DLC, verified toll-free and shortcode sender paths.
    • 1 August 2026 — Recorded the FCC cross-programme revocation waiver running to 31 January 2027, the 2025 vacatur of the one-to-one consent amendment, and treated +1 as a shared NANP code rather than proof of US jurisdiction.

    Last reviewed 1 August 2026

    Disclaimer

    This is operational guidance, not legal advice. Requirements vary by technology, federal and state law, sender type, provider, carrier, campaign, consent basis, message purpose and customer setup. Flowstates confirms the live path during onboarding.