Best 6 SIP trunking providers for small businesses

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.

Our research

To recommend the best phone systems for small businesses, our team of expert writers and researchers hone in on the most important factors. We rate providers on value for money – including initial setup costs, any equipment costs, and ongoing service fees; an ability to scale as your team grows; depth of features, plus the help and support options that are available.
Written and reviewed by:
Robyn Summers-Emler Grow Online Editor is reader supported – we may earn a commission from our recommendations, at no extra cost to you and without impacting our editorial impartiality.

We think the best SIP trunk provider for small businesses is TalkTalk Business thanks to its Quality of Service guarantee ensuring the best voice quality, and multiple disaster recovery plans. If you’re choosing SIP trunking as your preferred style of VoIP phone technology for your business, then TalkTalk is a great choice.

But, no two businesses are alike, and it’s essential you find the best value solution for your needs. Inflation has sent business costs skyrocketing – even for those who have ditched their traditional office setting for a flexible, remote working environment – which means it’s worth putting the time in to research the best deal from your SIP provider.

Best SIP Trunking Providers at a glance

  1. TalkTalk Business – best overall Sip Trunking provider
  2. BT Cloud Voice – a great choice for remote-working businesses
  3. Gamma – an excellent provider for scaling as your business grows
  4. Spitfire – a super solution if you need equipment as well
  5. Xinix – very affordable options for smaller teams
  6. Zen – excellent integrations and good customer feedback

Don’t overspend – you can click any of the links above to begin comparing fees on SIP trunking providers for your own business’s size and needs.

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.

You can also use the handy form, below, to compare costs from top providers in moments:

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SIP Trunk Providers 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.

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TalkTalk Business

BT Cloud Voice





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Call bundle or pay as you go plans

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£30 per month

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

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Remote working businesses needing a reliable, secure, cloud based SIP phone system

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

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

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Affordability, with cheap monthly costs for its plans, and reasonably priced product add-ons for international numbers

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

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TalkTalk Business

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

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).

Its pay as you go plans are tailored to each user’s specific needs. You’ll need to contact the sales team for specific quotes. Or, if you want to know exactly how much you’ll spend each month you can purchase a call bundle, starting at £120 for 1,000 calls, per month.

SIP is available for one or more trunks, along with the option to choose new numbers or transfer your current ones. In terms of security, multiple disaster recovery plans are also available. Spend management tools are available to monitor for fraudulent calls, which can be checked by the hour or by the day.

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

However, the platform doesn’t offer minutes or call bundles for international calling specifically, which could be a discriminating factor for small businesses that operate abroad.

Pricing from: Call bundle or pay as you go plans – contact provider

TalkTalk Pros
  • Call inclusive bundles are transparently priced, with scalable options depending on your business size
  • Internet, phone, and SIP are all available with this provider, giving you ultimate flexibility over your business operations
  • TalkTalk Business automatically checks for fraudulent calls by either the hour or day
TalkTalk Cons
  • No international package means that minutes or call bundles aren’t available for international calls specifically

BT Cloud Voice

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

BT is a household name in the UK, and is well-known for providing phone and telecommunications systems. Its website boasts claims of being used by 1.2 million businesses in the UK.

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.

Pricing from: £13 per month

BT Cloud Voice Pros
  • BT is an established and recognisable brand in the UK telecommunications industry
  • One phone number for all BT services makes it easy to get help
  • Can connect with other BT cloud features, such as conferencing facilities
BT Cloud Voice Cons
  • BT closed its SIP Trunk offering in November 2021, prematurely ending many business user contracts. Be wary that the provider is prone to making contract changes.


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

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, which means its quoted prices are not the most affordable on this list.

Pricing from: Contact provider

Gamma Pros
  • Gamma owns its own network which gives it more authority should any network issues arise
  • Provides access to wider services through partnerships with Janet and Semafone
  • Users get access to fraud protection at no additional cost
Gamma Cons
  • Customer support is limited, with no web support option available


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

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.

Pricing from: £4 per month

Spitfire Pros
  • Phone systems, data circuits, and SIP trunking (as well as other services) are all available from the same provider
  • UK and international locations available
  • Businesses can upgrade or downgrade their subscription plan in seconds.
Spitfire Cons
  • While Spitfire advertises itself as £4 per month, there are hidden fees attached to this, such as an added charge for line rentals


Best for: Affordability, with cheap monthly costs for its plans, and reasonably priced product add-ons for international numbers (£5 per month)

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.

Pricing from: £12 per month

Xinix Pros
  • SIP trunking services available without a long term contract
  • Voice and data services are billed together
  • 99.999% uptime guaranteed, so you can count on less than 26 seconds of downtime each month
Xinix Cons
  • Not all UK mobile providers are listed, which means you might need to pay extra for calls to alternative providers


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

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+.

Pricing from: £30 per month

Zen Pros
  • Technical team offer maintenance and management from the UK
  • Zen is an ITSPA member, and follows its strict guidelines for safe and secure VoIP services
  • Internet connection offered at a fast 100mbps
Zen Cons
  • Channels are only available in certain amounts, so you'll need to make a consistent amount of calls per month (not good for seasonal selling)
Still not sure which provider you should choose?

Compare quotes from SIP trunking providers in just one minute using our simple cost comparison tool. You’ll receive further information only from the providers most suited to your business needs.

How does a SIP trunking provider work?

When a business decides to utilize SIP trunking, they connect their phone system (PBX) to the SIP trunking provider’s network using an internet connection. This establishes a virtual link or “trunk” between the business’s phone system and the provider.

Once the connection is established, the business can make and receive calls using the internet instead of traditional telephone lines. Voice signals are converted into data packets and transmitted over the internet as digital information.

The SIP trunking provider manages the routing of these voice packets, ensuring they reach their intended destinations. This includes handling call setup, call termination, and call quality monitoring.

What types of business are SIP trunking providers suitable for?

A SIP trunking provider is suitable for a wide range of businesses, regardless of their size or industry. It caters to businesses that seek cost-effective and flexible communication solutions.

Small businesses and startups can benefit from SIP trunking services as they offer scalability, allowing businesses to adjust their communication resources according to their needs and budget.

Businesses with remote or mobile teams can benefit from the flexibility of SIP trunking, as it enables seamless communication over the internet, allowing employees to stay connected on the go.

And lastly, companies with international or multi-location presence can establish virtual phone numbers in various geographic regions, expanding their reach and enhancing customer engagement.

How did we find the best SIP Trunk providers?

In order to identify the top SIP trunk providers for SMEs, our team of experts used a combination of reader insight and our own analysis into this growing market.

Today’s business owners need to contend with rapid inflation and an increased cost of working from home. We looked at the pricing options available, alongside their compatibility with existing business technology, to determine each provider’s overall value for money.

Support hours was another key area for our researchers. It’s no good signing up to a provider that is only available for help while your offices are closed!

On top of this, we also looked at the security features available with each provider to ensure that small businesses and their customers are protected if revealing intimate information over the phone.

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.


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?


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.


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?


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.


According to a Technavio 2021 report, VoIP systems are projected to grow by £4.5bn between now and 2026. As SIP trunks become more competitive, they’ll also be more vulnerable to attacks.

Take a look at what security measures each service has in place to ensure that the service won’t pose a threat to, or compromise of, any other internet-based activity your business performs.


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.

Already have a SIP provider?

Check out 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.

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. is reader-supported. If you make a purchase through the links on our site, we may earn a commission from the retailers of the products we have reviewed. This helps to provide free reviews for our readers. It has no additional cost to you, and never affects the editorial independence of our reviews.

Written by:
Ross has been writing for Startups since 2021, specialising in telephone systems, digital marketing, payroll, and sustainable business. He also runs the successful entrepreneur section of the website. Having graduated with a Masters in Journalism, Ross went on to write for Condé Nast Traveller and the NME, before moving in to the world of business journalism. Ross has been involved in startups from a young age, and has a keen eye for exciting, innovative new businesses. Follow him on his Twitter - @startupsross for helpful business tips.
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