Written by Aimee Bradshaw Reviewed by James Macey Updated on 20 April 2023 On this page What is SIP trunking? SIP trunk providers in the UK 8×8 FlowRoute Net2Phone Free SIP providers in the UK How We Ranked the Best SIP Providers Expand Our site is reader-supported – by clicking our links, we can match you with a potential supplier, and we may earn a small commission for this referral. According to our research, the best SIP trunking providers are 8×8, FlowRoute, and Net2Phone.As VoIP (voice over internet protocol) phone systems become the norm, businesses have had to learn a new set of terminology. Session Initiation Protocol (SIP) is a standardised set of communication formats used in VoIP, instrumental in the sending of voice and video messages over a VoIP phone system. In recent years, SIP trunking has replaced standard phone system trunking, bringing a higher level of efficiency and quality to calls. Save by comparing telephone systems quotes from leading suppliers Do you already have a business telephone system? Yes No Just answer a few questions – it only takes a minute What is SIP trunking?Many business phone systems are hosted on a Private Branch Exchange (PBX), which eliminates the need for an individual line to be run to each desk in an office. To communicate with the outside world, businesses use trunking, which is in essence a pipe leading calls from the office to the public switched telephone network (PSTN).The PSTN network will be switched off by December 2025, which means phone lines will need to be switched over to a digital network.SIP trunking allows a business to make full use of an IP-based PBX, replacing traditional PSTNs with a PSTN from an internet-based SIP trunk provider. In the process, an SIP trunk can reduce a business’s overall costs and improve reliability for video conferences. For this reason, many businesses are making the switch.Learn more about the differences between SIP and VoIP on our page. SIP trunk providers in the UKBusinesses today can choose from a wide variety of SIP trunk providers, many of which offer affordable, high-quality services. 8×8 8x8 Pricing Bespoke Get free quotes 8x8 Review Quick overview 8×8 offers free point-to-point calling between a business and other 8×8-enabled sites, as well as unlimited concurrent calls. 8×8 also offers virtual numbers, which means local numbers can be set up in a variety of cities to make it easier for customers to call for assistance. The company’s SIP pricing is based on a business’s unique needs, with prices changing as a business grows and more numbers and features are added. Read more + Read less - FlowRoute FlowRoute Get free quotes Quick overview Developed by telecom-savvy developers, FlowRoute is designed to provide simplified, scalable, and direct access to a global network of VoIP users. FlowRoute offers phone numbers for £0.90 per month with outbound rates at £0.0070 per minute. The system uses detailed routing intelligence to manage calls for more advanced phone system functionality. Read more + Read less - Net2Phone net2Phone Get free quotes Quick overview Net2Phone is an internet-based calling service that works with any PBX phone, making it ideal for businesses that already have PBX equipment in place. The service offers unlimited concurrent calls, no monthly contracts, and high-quality, low-cost calling. Customers pay as they use the service, with simplified, per-minute pricing that might be more suitable to businesses with low call volumes. Read more + Read less - Free SIP Providers in the UKThere are several providers that offer free SIP trunking, but these services can be of poorer quality than paid services. However, if your budget is very tight you could consider one of the following options:OnSIP provides mobile and desktop voice and videoconferencing.SIP2SIP offers audio, video, presence, chat, file transfer, and conferencing.Antisip offers toolkits for mobile and desktop platforms.With so many excellent providers, businesses can shop around to find the best pricing and features to meet their needs.For organisations with existing PBX equipment, an option that works with the hardware already in place can save a great deal on initial set-up costs. How We Ranked the Best SIP ProvidersAt Expert Market, we spend time researching, testing, and evaluating providers we write reviews about. This typically consists of conducting market research to narrow down the software that's really worth digging into a little more and then assessing it against a range of research criteria.Informed by readers and businesses we speak to regularly as well as our own experiences using major VoIP platforms, we designed a research framework consisting of eight overarching assessment categories that we used to assess each VoIP provider.Scoring Criteria with Respective WeightingCall Management (25%): an analysis of a given platform's call management features, including call routing functionality and the presence of a virtual receptionist.Communication Channels (20%): assessment of the tools available within a VoIP platform for internal communication, including team messaging, video conferencing, and SMS capabilities.Training Features (20%): the ability of the VoIP service to support the training of employees, from call review features like call recording and call data reporting, to live call coaching features like call barge or call whisper tools.Pricing (10%): the pricing structure associated with the VoIP service, such as monthly subscription fees, call rates, setup fees, and any additional charges for add-on features or services.Software Integrations (10%): the VoIP service's ability to connect and integrate with external software systems, such as integration varying CRM, helpdesk, and external video conferencing platforms.Hardware Integrations (5%): the ability of a VoIP service to integrate with different phone brands.Customer Support (5%): the extent of assistance and resources provided by the VoIP service provider to customers including technical support, online resources, and access to customer support representatives.Security Options (5%): the measures and features implemented by the VoIP service to ensure the confidentiality, integrity, and protection of voice communications and data. Written by: Aimee Bradshaw Writer and researcher Aimee is Expert Market’s resident telephone systems and point of sale go-to. If she’s not writing about business products, you’ll find her daydreaming about dog walking on Dorset beaches. Reviewed by: James Macey Senior Business Software Researcher James draws on his 4+ years experience as a researcher to offer specialized advice on a wide range of categories from CRM to Fleet Management. He believes all businesses can grow if they use the right tools and services.