Written by Aimee Bradshaw Updated on 21 June 2022 On this page What is SIP trunking? SIP trunk providers in the UK SIP.US 8×8 FlowRoute Net2Phone Free SIP providers in the UK Expand According to our research, the best SIP trunking providers are SIP.US, 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.If you'd like help in finding the best phone system for your business, complete with SIP trunking, try our free quote-finding service. You'll be matched with the right providers for you, who'll be in touch with tailored, no-obligation quotes and answers to your questions. 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).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. 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. SIP.US With a free trial that includes an hour of free calls, SIP.US allows businesses to try its service out before committing. SIP.US’s edge is its high level of customer support. Instead of routing customers through a maze of tier-one, tier-two, and tier-three support, any problems go directly to a knowledgeable support representative with at least five years of experience with SIP trunking. 8×8 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. FlowRoute 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. Net2Phone 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. 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. 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.