Can you call 999 from a business VoIP phone in the UK?

Yes, a business VoIP phone can call 999 and 112, but only while it has mains power and a working internet connection. If the power or the broadband goes, the desk phone goes with it, so the safe set-up is a mobile within reach, a registered address that is correct for the number, and a rule everyone in the office knows.

That is the main thing you give up when you leave a copper line. I've worked in business telecoms since 2012, and I'd rather you hear it from me before you sign than find it out in a power cut.

Why does a VoIP phone stop working in a power cut?

A VoIP phone stops in a power cut because every part of the chain needs electricity at your end. The phone, the router and the broadband box all draw mains power. A copper landline was powered from the telephone exchange, which has its own backup, so a basic handset kept working when the building went dark.

Ofcom, the UK regulator, says the same in its guidance on protecting access to emergency organisations when there is a power cut at the customer's premises (opens in a new tab), published on 10 October 2018. It applies to providers whose customers call over broadband.

I covered the wider comparison in VoIP vs landline for a UK business. This article is only about emergency calls.

What does Ofcom expect a provider to do?

Ofcom expects a provider to have at least one solution that lets customers reach the emergency services for a minimum of one hour after a power outage at their premises. That is guidance built on General Condition A3, which requires providers to take all necessary measures to keep access to emergency organisations uninterrupted. It is not a promise that your office phones will run for an hour.

Three details in the guidance document (opens in a new tab) matter to a business:

• The free protection is aimed at customers who depend on their landline to reach the emergency services, such as someone with no mobile signal.
• It covers business customers too, and Ofcom expects providers to take the principles into account for them.
• Ofcom does not expect a provider to back up every line in a large office. A sole trader working from home, or a small office with no mobile signal, is the case where it expects a provider to act.

So the one-hour solution exists for people who have no other way to call. For a team with mobiles in their pockets, the mobile is the backup.

Does the 999 call know where my office is?

Not automatically. A VoIP number can be used from anywhere, so the emergency operator may not know where the caller is unless the provider passes on an address. For Olatti, the address you register for each number is the one sent, so you must keep it current. If someone calls from another site, they have to give the operator their location.

This is in section 8 of the Olatti terms. It is the check I'd run first with any provider: ask where the registered address is stored and who in your business updates it when you move desks or floors.

Does Olatti still allow 999 calls if my credit runs out?

Yes, with one exception. Running out of Credit, going over an allowance or a fair-use action never blocks an emergency call. Olatti's terms do say emergency calls may not work while an account is suspended or before a number is fully provisioned, so a new number should not be the first thing you test on an emergency.

Olatti is prepaid, and if Credit runs out chargeable outbound calls stop. Inbound calls, calls to colleagues and emergency calls carry on. The plans and what they include are on the pricing page.

What should a small office set up?

Set up three things: a charged mobile within reach of every desk, a correct registered address, and one written line telling staff what to do. Then add backup power only if your phones really are the only way anyone can call out.

1. A mobile that is not on your office broadband. A mobile on a mobile network keeps working when your router does not. This is the backup Olatti's terms tell you to keep.
2. An address you have checked. Look at the registered address for each number when you move, add a site or change a desk. Put the check on whoever manages the account.
3. One sentence in the staff guide. "If the power or internet is down, call 999 from a mobile." Nobody should work that out for the first time during an emergency.

Battery backup, where it earns its place. A small uninterruptible power supply on the router and the desk phone can keep a desk running for a while. It is worth having for a reception desk with no mobile signal. It is not worth buying for every seat.

The PSTN switch-off checklist has the same question in the list of things to ask before you move.

What about a mobile line from Olatti?

Olatti's optional eSIM, available by registering interest, puts your business number on the person's own mobile as a second line, and emergency calls on that line go over the mobile network in the usual way. That is different from the app and desk-phone calls, which use the internet. If a team is out on sites, this is the one that doesn't depend on broadband. The details are on the eSIM page.

A desk phone still earns its place at reception and shared desks, and which Yealink desk phone to buy goes through the options. Just don't treat it as your only way to dial 999.

Frequently asked questions

Can a business VoIP phone call 999? Yes, while it has power and a working internet connection. Without either, it can't, so keep a mobile within reach.

Does a VoIP phone work in a power cut? Not on its own. The phone, router and broadband equipment need mains power. A battery backup can keep them running for a limited time.

Does Ofcom require battery backup for business VoIP? Ofcom's 2018 guidance expects providers to have a solution that gives at least one hour of emergency access, free to customers who depend on their landline. It does not expect every line in a large office to be backed up.

Will the emergency services see my office address? Only if the provider passes it on. With Olatti, the registered address for the number is sent, so keep it up to date and be ready to say your location if you call from somewhere else.

Does the Olatti eSIM call 999? Yes. Emergency calls on the eSIM line go over the mobile network.

If you're choosing a system, the business phone system page covers what Olatti does and what it costs.