compliance
STIR/SHAKEN is a US caller ID authentication standard that lets phone carriers digitally sign calls. This proves the caller ID has not been spoofed. As of July 2026 it has been mandatory for major US voice providers since June 2021.
STIR (Secure Telephone Identity Revisited) and SHAKEN (Signature-based Handling of Asserted information using toKENs) work together so the originating carrier attaches a cryptographic signature to a call. The receiving carrier then checks it before the call rings through.
Calls get one of three attestation levels. Level A is full attestation, where the carrier vouches for the caller and the number. Level B is partial, where the carrier knows the caller but not that they own the number. Level C is gateway, where no verification is possible. Full attestation calls are far less likely to be flagged as spam.
The UK has no direct STIR/SHAKEN equivalent as of July 2026. Ofcom instead requires network-level measures against number spoofing and is developing its own caller authentication framework. This means the UK situation differs meaningfully from the US mandate.
Worked example
A 4-person business switches from an unverified VoIP provider to one with full STIR/SHAKEN attestation.
Their outbound calls stop showing as "Spam Likely" on customers' phones within about a week of the switch.
Why it matters to a small team
A small business whose calls carry weak or no STIR/SHAKEN attestation risks having every outbound call flagged as spam to customers. This quietly kills answer rates. Choosing a provider that fully attests calls is a free way to protect deliverability.
Yes, the FCC has required major US voice service providers to implement STIR/SHAKEN since June 30, 2021, with smaller providers given extended deadlines. As of July 2026 it remains a binding US requirement, not a voluntary standard.
It does not block spam calls directly, but it makes caller ID spoofing detectable, which carriers use alongside spam-labeling systems to flag suspicious calls, reducing (not eliminating) fraudulent caller ID use.
This usually happens when a number has low or partial STIR/SHAKEN attestation, high call volume flagged by carrier algorithms, or has previously been reported by recipients, regardless of whether the calls are legitimate.
Not as of July 2026. Ofcom requires carriers to take steps against number spoofing but has not mandated a token-based signing standard equivalent to the US STIR/SHAKEN framework; a UK-specific approach is still developing.
One app, your number, calls logged to your CRM. Per-user pricing, no minimums. Free for 7 days, working in minutes.
7-day free trial. No card required. Cancel anytime.
7 days free, no card required. Tell us about your setup and we'll have your number ready in minutes.