If your traffic has always been UK, the US looks familiar until the first invoice. The technology is the same SIP you already send; the commercial and regulatory shape underneath it is not.
One rate becomes three
UK termination splits mainly by landline and mobile. US termination splits by jurisdiction, and the distinction is regulatory rather than technical:
- Interstate — the call crosses a state line. Usually the cheapest.
- Intrastate — caller and called party are in the same state. Usually dearer, sometimes markedly.
- Local — within the same rate centre.
Which one applies is decided by the relationship between your caller ID and the number you dial, not by where you are sitting. That means your own CLI choice moves your costs, which takes UK operators a while to get used to.
Be careful with a single blended rateA provider quoting one US figure is averaging interstate and intrastate across some assumed mix. If your traffic is more intrastate than that assumption, you pay for the difference. Ask for both numbers.
Toll-free runs backwards
In the UK, inbound to an 0800 costs the number’s owner. In the US the principle is the same but the wholesale economics work in your favour: traffic arriving on your 800, 833, 844, 855, 866, 877 or 888 numbers generates a payment to the carrier terminating it.
If a meaningful share of your business is US inbound, that is not a footnote — it changes whether a deal is worth doing. Raise it when you ask for rates rather than after.
Numbering is organised differently
UK geographic numbers map to area codes you can reason about. US numbering runs on area code plus rate centre, a smaller unit that decides what counts as local. Two numbers in the same area code can sit in different rate centres and bill differently.
Practical consequence: when you buy US DIDs, specify the rate centre, not just the area code. A number in the right area code but the wrong rate centre looks local to your customer and does not bill as local to you.
Caller ID is verified now
The biggest operational difference. US carriers cryptographically sign calls under STIR/SHAKEN, and anything they cannot vouch for gets labelled on the recipient’s screen.
A UK operator sending to the US through a gateway typically gets the lowest attestation level and the labelling that comes with it. The fix is to originate with a carrier that issued your US numbers and can attest for them — there is a fuller explanation here.
Registering your name is worth doing
CNAM shows your business name on US handsets beside the number. It is a small setup task and it lifts answer rates more than most things you could spend the same hour on, because a named call is answered and an unknown number is not.
What stays the same
Everything technical. The same SIP trunk, the same codecs, the same G.711 you should already be using, the same failover thinking. If you run Asterisk, adding US destinations is dialplan work rather than a project.
And the commercial questions worth asking are the ones you already ask about UK routes: is it a direct route, what ASR does it run at, is CLI passed through unchanged, and what happens when the first carrier fails.
US routes on the same account, the same balance and the same terms as your UK traffic.
See our US routes
