STIR/SHAKEN for small business
Your outbound calls keep getting flagged as “Scam Likely” or going straight to voicemail. STIR/SHAKEN is the reason — and the fix. A plain-English guide to how verified caller ID works, what the A/B/C attestation levels mean, and how to make sure your small business calls actually get answered.
The core problem
Two calls. One gets answered.
Here's what the same outbound business call looks like on the recipient's phone, depending on whether your provider signs the call with STIR/SHAKEN A-level attestation.
Without STIR/SHAKEN signing
Incoming call
Scam Likely
(512) 555-0194
- Recipient sees a warning label, not your business name
- Answer rates drop to 11–25% in most industry studies
- Voicemails get ignored by default
With STIR/SHAKEN A-level
Incoming call
Austin Plumbing Co.
(512) 555-0194
- Recipient sees a verified business call
- Answer rates climb back toward 50%+
- Voicemails are trusted, follow-ups get returned
Definition
What STIR/SHAKEN actually is
STIR/SHAKEN is a set of technical standards and industry protocols that lets phone carriers cryptographically sign outbound calls with information about who originated them. The receiving carrier can then verify that signature and decide how to display — or filter — the call on the recipient's phone.
STIR stands for Secure Telephone Identity Revisited — the IETF standard that defines how calls get cryptographically signed. SHAKEN stands for Signature-based Handling of Asserted information using toKENs — the ATIS industry framework that specifies how North American carriers implement STIR on their networks.
In the US, the TRACED Act (Telephone Robocall Abuse Criminal Enforcement and Deterrence Act of 2019) gave the FCC authority to require STIR/SHAKEN across most voice providers. The compliance deadline for larger providers was June 30, 2021. Canada's CRTC has a parallel framework with the same goal.
In practice: every time you make an outbound call in the US or Canada today, your carrier either signs it with an attestation level (A, B, or C) or doesn't sign it at all. The recipient's carrier then makes filtering and display decisions based on that signal — plus reputation scoring, complaint history, and other behavioral factors.
The A/B/C system
The three attestation levels
Not all signed calls are equal. Here's what each level actually means, who gets each, and how recipients' phones treat them.
Level A
Full attestation
What it means
Originating carrier has verified both the caller's identity and their right to use the number.
How it displays
Call shows as verified on recipient's phone. Highest chance of being answered.
Typical example
A VeraDial number you purchase directly: VeraDial (via Twilio) attests to your identity and your authorization to use the number.
Level B
Partial attestation
What it means
Carrier has verified the caller's identity but not their authorization to use the specific number being displayed.
How it displays
Call is signed, but the recipient's carrier may still apply mild filtering. Better than unverified, not as trusted as A.
Typical example
A number you already own that you've verified with VeraDial as a secondary caller ID — voice only.
Level C
Gateway attestation
What it means
Carrier passed the call through but can't verify identity or authorization (typically international or older infrastructure).
How it displays
Carriers and phone OS's may flag the call as "Scam Likely," "Spam Risk," or simply "Unknown."
Typical example
A generic VoIP service that routes through a gateway without signing, or international calls that enter through a legacy provider.
Why small businesses care
What STIR/SHAKEN means for your business
For a solo operator or a small team, attestation level is one of the highest-leverage things you can influence about your outbound calling. It determines whether your calls feel like business-as-usual or feel like spam.
Answer rates collapse when calls look suspicious
Industry research consistently shows answer rates of 11–25% for calls displayed as "Unknown" or "Scam Likely," vs. 50%+ for verified business calls. If you're an owner-operator trying to reach new customers, this is the difference between a full week of appointments and a week of voicemails.
Your brand gets tied to a spam label
When a prospect sees your number show up as "Spam Risk," that association sticks even after they find out it's a legitimate business. Your callback gets ignored. Your follow-up gets declined. You're fighting against your own number.
Compliance with the TRACED Act
The TRACED Act (2019) required US voice providers to implement STIR/SHAKEN by June 2021. Carriers now actively filter unsigned or weakly-signed traffic. If your phone provider isn't set up for A-level attestation, you're downstream of that filtering — and there's nothing you can do about it from your end.
Texts and voicemail don't fix the trust gap
You can't follow up with a text from a number the recipient doesn't trust. You can't leave a voicemail that gets listened to if the phone rang as "Scam Likely." Verified outbound voice is the foundation — every other channel from that number inherits the trust (or lack of it).
Diagnose your setup
How to check what level your calls are signed at
Three quick ways to figure out whether your current business number is getting A, B, or C attestation — or no signing at all.
Call a colleague on a different carrier
Dial someone you know on a different carrier from yours. Ask what the display shows: your business name, "Unknown," "Scam Likely," or a clean phone number with no label. If it's anything other than a clean name-and-number display, your calls aren't being trusted.
Use a carrier-branded lookup
Install your carrier's spam-filtering app (AT&T ActiveArmor, Verizon Call Filter, T-Mobile Scam Shield). Many will report the attestation level of incoming calls in-app. Call yourself from the number in question and check the result.
Check with your provider directly
Ask your current phone provider (cell carrier, VoIP service, or app) what attestation level they sign your outbound calls at. An honest answer should be A, B, or C — or "we don't sign calls at all," which is the worst-case. Anyone who can't answer probably isn't doing it.
Where providers fall short
Common gaps in small-business phone setups
If your outbound calls keep landing in spam despite a paid business phone app, one of these is usually why.
Free or ad-supported apps
TextNow, Hushed, Burner, most free-tier services
These run on pooled/recycled VoIP infrastructure with no carrier-level customer authorization. Even if they sign something, it's typically C-level or not signed at all.
Second-line apps that don't market attestation
Sideline, Line2, many budget VoIP apps
If a provider doesn't explicitly mention STIR/SHAKEN A-level attestation in their documentation, they probably don't offer it. Modern providers who do offer it actively promote it because it's a meaningful differentiator.
Caller ID spoofing tools
SpoofCard and similar
These services are the opposite of STIR/SHAKEN — they try to display a number that isn't yours. Carriers increasingly block these outright, which is the point of the system.
Unmanaged BYOD setups
A personal cell used for business without verification
Your cell number is signed by your carrier, but if you're using it for business calls that don't match your carrier profile (lots of outbound, unfamiliar contacts), your own carrier's reputation scoring may degrade over time.
How VeraDial handles it
A-level attestation on every purchased number
Numbers purchased through VeraDial are provisioned on Twilio's carrier-grade, STIR/SHAKEN-compliant voice infrastructure. We verify your customer identity and attest to your authorization for the number, which gives your outbound calls A-level attestation. No extra configuration, no per-minute premium — it's included in the $9.99/mo plan.
If you already have an existing number (your cell number, a Google Voice number, a toll-free you own), you can verify it in VeraDial and use it as a secondary outbound caller ID. Verified numbers receive B-level attestation on outbound voice calls. SMS is not supported on verified numbers — that channel requires a VeraDial-provisioned number for carrier compliance reasons.
FAQ
STIR/SHAKEN questions, answered
What is STIR/SHAKEN?
STIR/SHAKEN is a framework of technical standards and industry protocols that lets US and Canadian phone carriers cryptographically sign outbound calls with information about who originated them. STIR (Secure Telephone Identity Revisited) defines the signing standard; SHAKEN (Signature-based Handling of Asserted information using toKENs) defines how carriers implement it across their networks. Together they let the receiving carrier know whether an incoming call came from a verified source or not, so filtering and display decisions can be made automatically.
Is STIR/SHAKEN mandatory?
For US voice providers, yes. The TRACED Act (Telephone Robocall Abuse Criminal Enforcement and Deterrence Act) passed in 2019 and the FCC mandated STIR/SHAKEN implementation for most voice providers by June 30, 2021. Smaller providers got extensions, but those have largely expired. In Canada, the CRTC has implemented similar requirements. For business owners making calls, the system is fully in effect whether you realize it or not — you're already being filtered by it.
What are the A, B, and C attestation levels?
A (full attestation) means the originating carrier verified both the caller's identity and their authorization to use the specific phone number. B (partial attestation) means the carrier verified the caller but not their authorization for that exact number. C (gateway attestation) means the call was passed through without identity verification — typically international calls or traffic routed from legacy networks. Carriers and mobile OSs treat A-level as verified, B-level as mostly trusted, and C-level as suspicious (often leading to "Scam Likely" labels).
Does STIR/SHAKEN stop robocalls?
Not directly — STIR/SHAKEN doesn't block calls. What it does is make spoofing harder and give receiving carriers reliable signals to apply their own blocking and labeling decisions. Most consumer call-blocking features on iOS and Android, plus carrier-level spam filters, rely on STIR/SHAKEN signatures to decide whether to let a call through cleanly, label it as suspicious, or filter it entirely. Legitimate robocalls (like your pharmacy's refill reminders) signed at A-level will still reach you; unverified spoofed calls won't.
Can I get STIR/SHAKEN attestation on my existing number?
It depends on your provider. Your regular mobile carrier (Verizon, AT&T, T-Mobile, Rogers, Bell, Telus) will sign your outbound calls automatically at A-level because they provisioned your number. If you use a VoIP or business phone service that lets you "bring your own number," most will only sign those calls at B-level at best — because they can verify you as a customer but can't verify your authorization for a number issued by a different provider. VeraDial offers B-level attestation on verified existing numbers for voice only.
Why do my calls still show as "Scam Likely" even if my provider supports STIR/SHAKEN?
STIR/SHAKEN is a strong signal but not the only one carriers use. Reputation scoring based on call volume, contact diversity, spam complaints, and behavioral patterns also feeds into labeling decisions. A new business number calling many unfamiliar contacts can get temporarily flagged even with A-level attestation. If you're seeing persistent "Scam Likely" labels, check (a) your attestation level, (b) your number's age and history, (c) whether a prior owner had reputation issues, and (d) whether you can register your business with carrier reputation portals like Free Caller Registry.
Does STIR/SHAKEN cost extra?
For most carriers and modern business phone services, STIR/SHAKEN signing is included in the base service — it's required by regulation so providers don't charge extra for it. What does vary is whether a provider offers A-level (versus B or C). VeraDial's $9.99/mo subscription includes A-level attestation on every purchased number at no extra cost.
What attestation level do VeraDial numbers use?
Numbers purchased through VeraDial carry STIR/SHAKEN A-level attestation. The underlying infrastructure (Twilio) is registered as the authoritative voice provider, VeraDial verifies your customer identity, and we attest to your authorization to use the number because we provisioned it to you. If you bring an existing number and verify it as a secondary outbound caller ID, that receives B-level attestation on voice calls only (SMS is not supported on verified numbers).
Does STIR/SHAKEN work on text messages?
No — STIR/SHAKEN is a voice-call framework. Text messages have a separate set of anti-spoofing and reputation controls handled by the major carriers and the Campaign Registry. If your SMS from a business number is getting filtered or blocked, the issue is different: typically it's about A2P (application-to-person) registration, message content, and throughput patterns rather than cryptographic signing.
Looking for product-specific answers? See the full VeraDial FAQ →
Stop losing calls to spam labels
Get verified outbound calling.
VeraDial gives you a dedicated business number with A-level STIR/SHAKEN attestation on every outbound call — plus AI calling, call recording, SMS, and voicemail transcription. All for $9.99/mo with a 3-day free trial.
iOS coming soon
Informational overview of STIR/SHAKEN for small business operators. Attestation outcomes on specific calls can vary based on receiving carrier, reputation scoring, and other factors outside any single provider's control. Current as of April 2026.