Best six SIP trunking providers for small businesses in 2021

Interested in using SIP trunking in your small business? Want to discover who the best SIP trunk providers in the UK are? Read on to find out more...

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There are many SIP trunking providers for small businesses to choose from, and some of the best SIP trunking providers in the UK include BT, Gamma, Spitfire, TalkTalk Business, Xinix, and Zen.

For us at Startups, the best SIP trunk provider for small businesses is TalkTalk Business. This is for a number of reasons, including its dedicated 24/7 UK-based support team, the Quality of Service guarantee ensuring the best voice quality, and its multiple disaster recovery plans.

But, no two businesses are alike, and it's essential you find the best value solution for your needs. If your business is looking to save money by investing in SIP trunking, the best way forward is to complete our custom-built comparison tool and receive personalised quotes that can help you save.

SIP trunking is becoming ever more popular, as the need for analogue lines becomes redundant for many businesses who have ditched their traditional office setting for a flexible, remote working environment. It also greatly reduces call costs, which after the turbulent eighteen months small businesses have had, is a huge benefit for those aiming to cut their overheads.

However, despite TalkTalk Business being the best SIP trunking provider in our opinion, that doesn’t mean it will necessarily fit the needs of your business. In this expert guide, we review the top providers to help you make an informed decision. We compare across a number of key metrics, including cost, network ownership, the number of services or features offered, and best practices.

Read on to find out more about the six best SIP trunking providers in the UK. 

Already clued up on SIP trunking providers?

If you are feeling confident about the pros and cons of each provider already, and want to save yourself time reading through our in-depth review, why not use our custom-built comparison tool to compare quotes from providers directly?

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SIP Trunk Providers: At-a-glance comparison

When choosing a SIP trunk provider, it can be difficult to know which factors should affect your decision. Whether you’re looking for a reliable network and solid infrastructure, more interested in keeping costs down, or making best practice your top priority, our list of the best SIP trunking providers in the UK will help you navigate the process.

The best SIP Trunking Providers of 2021

ProviderBest forSetupPricing from
BTRemote working businesses needing a reliable, secure, cloud based SIP phone systemFree
£13 per month
GammaBusinesses needing flexibility to upsize or downsize lines whilst retaining the same contact numbersFree
Contact provider for quote
SpitfireSmall businesses wanting an end-to-end business phone solution - including phone system, data circuit and SIP all managed together Free
£4 per month
TalkTalk BusinessBusinesses requiring a high level of customer support, with 24/7 support available from UK-based agents. Free
Call bundle or Pay-As-You-Go plans – contact provider for quote
XinixAffordability, with cheap monthly costs for its plans, and reasonably priced product add-ons for international numbers (£5 per month). Also 30 day free trial. Free£4 per month
ZenIntegration with a number of telephone based systems, including Mitel, Avaya and 3CX£25 connection fee
£30 per month

All pricing is correct as of 16th August 2021 


The Best SIP Trunk Providers: A deep dive

Here, we take a closer look at each of our top six best SIP trunk providers, examining what they offer and why they made our list, as well as their pros and cons.

BT

bt

BT ProsBT Cons
Well-known company – BT is an established and recognisable brand in the UK telecommunications industry
Network – BT owns its network, giving it greater access and control
Centralised customer support – one phone number for all BT services makes it easy to get help
Cloud-based SIP – can connect with other BT cloud features
Company size – BT is a big organisation, so small businesses could feel like they’re not getting a personalised service

BT is a household name in the UK, and is well-known for providing phone and telecommunications systems.

It’s easy to contact customer support through a central help desk – so if you use BT for your business’ broadband and/or phones as well as for your SIP trunk in the UK, you can contact the support team on one phone number.

BT offers unlimited data and static IP addresses, while gateways are available if you’re not using BT phones. BT can also provide phone systems if your business doesn’t already have them set up.

The company offers cloud-based SIP, enabling it to connect with BT’s other cloud features for improved connectivity across resources and systems. Plus, this offers the other more general benefits of cloud technology, such as improved security and no need for wires.

BT owns its network, and is perhaps one of the most recognisable telecommunications companies in the country.

With that said, since BT is such a big company, it could be easy for a startup to feel like it’s not getting a personalised service – although BT says it does offer personal contact.

BT is best for: remote working businesses needing a reliable, secure, cloud based SIP phone system

Pricing from: £13 per month


Gamma

gamma

Gamma ProsGamma Cons
Owns its network – this gives Gamma more authority should any network issues arise
Partnerships – provides access to wider services through partnerships with Janet and Semafone
CallGuard – fraud protection at no additional cost
Award-winning infrastructure – won ‘Best VoIP Infrastructure’ at the 2016 and 2017 ITSPA Awards
General SIP trunking – there doesn’t seem to be a dedicated small business offering

Gamma is an established provider of SIP trunking, and owns its own national network. Gamma’s partnerships are one of the reasons it stands out: for example, Gamma is a Janet connected partner (the network for UK research and education institutions).

As well as this, it offers PCI DSS compliance through another partner, Semafone. PCI DSS (Payment Card Industry Data Security Standard) refers to the security standards for taking card payments. In a SIP context, this could apply to a call centre taking payments over the phone.

Gamma’s SIP trunks have also been tested and approved to integrate with Skype for Business, while its CallGuard feature offers free protection against fraud.

Gamma even won ‘Best VoIP Infrastructure’ at the 2016 and 2017 Internet Telephony Services Providers’ Association (ITSPA) awards, the UK trade association for the internet telephony industry.

However, it doesn’t seem to have a dedicated small business offering.

Best for: Businesses needing the flexibility to upsize or downsize lines whilst retaining the same contact numbers

Pricing from: Contact provider


Spitfire

spitfire

Spitfire ProsSpitfire Cons
Network ownership – can easily control and access its network
Affordable – SIP trunking pricing is clear and affordable
End-to-end service – phone systems, data circuits, and SIP trunking (as well as other services) are all available from the same provider
Phone numbers – UK and international locations available; it’s possible to keep your old number
Not a SIP trunking specialist – Spitfire can provide other services, like internet, data, and engineering products, meaning it doesn’t focus solely on SIP trunking

Like BT and Gamma, Spitfire also owns its network. It offers an end-to-end service, meaning it can provide your business with a phone system, data circuit, and SIP trunking.

Number porting is available, with the majority of the main voice providers supported. This means you can keep your existing phone number if you already have a phone system set up. Spitfire can provide SIP trunks for UK and international phone number locations, too.

However, since Spitfire offers a range of other services – including internet, data, and engineering products – this means it doesn’t specialise in SIP trunking alone.

Best for: Small businesses wanting an end-to-end business phone solution – including phone system, data circuit and SIP all managed together

Pricing from: £4 per month


TalkTalk Business

talktalk business

TalkTalk Business ProsTalkTalk Business Cons
Easy to understand pricing plans – PAYG and call inclusive bundles are clear and familiar
Multiple services – internet, phone, and SIP are all available
Customer support – UK-based and 24/7
Spend management tools – check for fraudulent calls by the hour or day
No international package – minutes or call bundles aren’t available for international calls specifically

TalkTalk Business offers businesses SIP trunking through pay-as-you-go (PAYG) or call inclusive bundles. It provides Quality of Service (QoS), meaning that voice traffic is prioritised over other data to ensure the best call quality (when using TalkTalk Business Ethernet data circuits).

Spend management tools are available to monitor for fraudulent calls, which can be checked by the hour or by the day.

SIP is available for one or more trunks, along with the option to choose new numbers or transfer your current ones. Multiple disaster recovery plans are also available.

TalkTalk has customer support and technical assistance that’s based in the UK, and is available 24/7.

It offers multiple services including internet, phone, and SIP – all from a well-established company.

However, it doesn’t offer minutes or call bundles for international calling specifically.

Best for: Businesses requiring a high level of customer support, with 24/7 support available from UK-based agents

Pricing from: Call bundle or Pay-As-You-Go plans – contact provider


Xinix

xinix

Xinix ProsXinix Cons
Reliability – 99.999% uptime guaranteed
Flexibility – SIP trunking services available without a long term contract
One bill – voice and data services are billed together
International calls – options and pricing for UK, Europe, and worldwide
Call rates – not all UK mobile providers are listed

Xinix provides SIP trunking services without a long term contract, and guarantees 99.999% uptime. Better still, all voice and data services are documented in one bill.

Xinix operates its own core network infrastructure, which supports the SIP trunk services on offer. It also provides clear, easy to understand UK and international call rates.

Xinix is great for international calls, offering options and pricing for the UK, Europe, the Americas, and the rest of the world in varying combinations. The packages are provided in clear and recognisable minute-based formats.

One issue, though, is that Xinix’s call rates information doesn’t feature the widest range of different UK mobile providers.

Best for: Affordability, with cheap monthly costs for its plans, and reasonably priced product add-ons for international numbers (£5 per month). Also a 30-day free trial

Pricing from: £4 per month


Zen

zen

Zen ProsZen Cons
Specialist help available 24/7 – technical team offer maintenance and management from the UK
Best practice – Zen is an ITSPA member, and follows its guidelines for safe and secure VoIP services
Vendor partnerships – official interop status with Snom, Mitel, Avaya, UM Labs, ShoreTel, and 3CX
Internet connection – offered at 100Mbps
Less flexible channel options – channels are available in certain amounts

Zen offers fraud protection that’s matched to your business level. It can provide broadband or leased lines to connect your phone system and SIP. Zen also has official interop status with the following vendors: Snom, Mitel, Avaya, UM Labs, ShoreTel, and 3CX.

Its network offers 100Mbps internet connection, with maintenance and management of the networks carried out by specialists who are based in the UK. Anytime customer support and technical assistance are also available as another option.

Zen is a member of the Internet Telephony Service Providers’ Association (ITSPA), the UK association for internet telephony providers. It follows ITSPA’s guidelines for operating VoIP services safely and securely.

As a member of ITSPA, Zen follows the organisation’s guidelines for operating VoIP services to the highest standard.

However, Zen has less flexibility than other providers, with the number of channels going up in set amounts: up to eight, 10, 15, 20, 30, and 31+.

Best for: Integration with a number of telephone based systems, including Mitel, Avaya and 3CX

Pricing from: £30 per month


Already feel confident in your knowledge of the best products available? Then maybe your best option is to compare quotes from SIP trunking providers right now, to save time.

Just fill out a few simple questions for our comparison tool, and you'll receive further information only from the providers most suited to your business needs.

Tips for choosing the best SIP trunk provider for you

With so many providers on the market, how do you tell them apart? And which aspects are essential to consider during the decision-making process? In this section, we offer our top tips for choosing the best SIP trunk provider for your small business.

Reliability

Whichever provider you opt for, make sure they’re reliable. This means assessing how the SIP service is delivered – for example, does the provider own its network? And what level of uptime does it offer?

Support

Whether it’s to help during installation, or to troubleshoot an issue further down the line, it’s likely you’ll need some help to use the SIP trunk effectively. And that’s where the support that a provider offers is critical — review where support agents are located, as well as how you can reach them, and what type of assistance they can provide.

Scalable

One of the main benefits of SIP trunking is how easy it is to add or remove lines as and when required. Be sure to choose a provider that makes this process as smooth as possible — for example, how flexible are their packages?

Pricing

When reviewing pricing, it’s useful to assess what is and isn’t included in each plan. Are there any additional charges? How transparent is the pricing structure? Consider these points to help you to work out which provider is really the best for your business and your budget.

Security

As SIP trunks run via an internet connection, you’ll need to ensure that the service won’t pose a threat to, or compromise of, any other internet-based activity your business performs. Take a look at what security measures each service has in place.

Compatibility

If you have existing phone systems equipment that you’re planning to use in conjunction with a SIP trunk service, find out if the provider will determine if the systems are compatible, and what the potential next steps are if they’re not.

Check out this article by GetVoip to learn more about choosing the right SIP trunk provider and the benefits of SIP trunking.


As you are looking at SIP trunking providers, why not read our review of the best office phone systems to help you choose the perfect handsets.

Next steps: Compare SIP Trunk Providers

At this stage, you’ve learned more about the different options available when choosing SIP trunks in the UK for your small business.

We’ve covered some of the best SIP trunk providers in the UK, as well as highlighting what to consider when making the decision and the benefits of opting for a SIP system.

As we mentioned earlier, our best SIP trunking service for small businesses is ultimately TalkTalk Business, with its 24/7 UK-based customer support, numerous disaster recovery plans if your internet goes down, and spend management tools to monitor fraudulent calls by the hour.

Although if you are a small business operating internationally, you'll be best to choose Xinix as your provider, which is the most cost-effective and affordable option on this list, offering an add-on for calling international numbers for only £5 per month.


What if I'm still stuck choosing between two providers?

We've done our best to summarise the best SIP trunking providers for small businesses, listing their features and highlighting their pros and cons.

And although we can't choose your provider for you, our team of experts have put together an incredible comparison tool to help you choose the right service for your business, even if you are torn between two of them.

Just fill out a few details, and we will get back to you with quotes and additional information.

Ross has been writing for Startups since May 2021, specialising in sustainable business and telephone systems. He also runs the successful entrepreneur's section of the website.

He's previously written for Conde Nast Traveller and the NME and is passionate about music, sustainability, and travelling. Follow him on his Twitter - @startupsross for helpful business tips.

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