The TTNC SIP Trunk service provides an IP connection between our network and your PBX over the Internet. This gives your PBX access to the public switched telephone network (PSTN) allowing you to make and receive calls

You can create SIP Trunks instantly and manage them in the cloud via our platform, myTTNC. This will give you dynamic call capacity, improved resilience and access to a wide range of hosted call management services.

We support connections ranging from two channels for small PBX equipped businesses, to an unlimited amount of channels for call centres and enterprise customers.



per month


Add Channels


per channel
Add to basket

  • Advanced cloud platform

    Scale and provision instantly

    Provision numbers and services instantly. Scale your call capacity at anytime by adding or taking away the number of channels you use

  • Advanced cloud platform

    Advanced SIP Trunk management

    Create user credentials and ACLs for SIP Registration and Static IPs. Mix PBX endpoints and standalone IP phones using SIP registration

  • Advanced cloud platform

    CLI and Number flexibility

    Manage your CLI presentation and numbers for outbound calls. Choose from over 7 million UK numbers or migrate your existing number to us

  • Advanced cloud platform

    Save money

    Benefit from free calls between offices and workers using our SIP Trunking service, a reduction of ISDN line rental and lower ongoing call charges

  • Advanced cloud platform

    Reliable business continuity

    Our SIP Trunking provides better business continuity than ISDN and includes disaster recovery (DR) and automatic failover features as standard

  • Advanced cloud platform

    Integrated Hosted Telephony

    Combine SIP Trunking with our advanced hosted telephony services such as Call Recording, Voicemail, IVR menus and Call Management services

What do you need and how does it work?

You'll need an IP enabled PBX, a TTNC phone number and an Internet connection.

  • After adding a SIP Trunk to your account, you need to configure it in the myTTNC portal.
  • This is when you assign the outbound Caller ID and set up the authentication method for your PBX. It's a straightforward process and shouldn't take longer than one or two minutes.
  • Once the SIP Trunk has been configured and set up on your PBX, you can forward any of your TTNC phone numbers to the SIP Trunk. We also provide automatic failover to PSTN, so you can choose to have incoming calls automatically forwarded to another destination (PBX, landline or mobile) if your PBX loses its Internet connection.
  • You can change the Caller ID whenever you want and use any of the numbers in your account. You can even present your own number (once we’ve verified it).

Please note: A TTNC number is still required when displaying a registered CLI.

Why use TTNC?

  • Providing VoIP services for more than 15 years
  • 16,000 businesses already use our services
  • Range holder of over 7 million phone numbers
  • UK owned and operated with 24/7 support
  • Multi-Award-Winning VoIP service
  • Comms Council member and regulated by Ofcom
  • Ofcom approved Code of Practice

SIP Trunk Pricing

SIP Trunk (including 2 inbound channels) Cost
Monthly cost £4
Additional inbound channel £2

Inbound Call Charges

Inbound Number / Pay As You Go (PAYG) Rate
01, 02, 03 and 07 Numbers
084 Service Numbers Free
0800 and 0808 Freephone Numbers £0.02/min* (2p)
International Numbers £0.02/min (2p)
International Toll Free Numbers £0.04/min (4p)

* Price is for calls originating from UK landline; add £0.025/minute (2.5p) for calls originating from UK mobiles.
Calls from UK Payphones are not accepted unless requested and cost an additional £0.85/minute (85p).

Calls to an 01, 02, 03 and 07 number forwarding to any other SIP address costs £0.01 (1p) per minute.
Calls to an 0800 number forwarding to any other SIP address is £0.035/minute (3.5p).

Outbound Call Charges

Pay As You Go (PAYG) is great if your call volumes are lower or unknown. Pay Monthly is ideal for those who spend a lot of time on the phone and want our lowest call rates.

Pay As You Go (PAYG)

Top up Amounts Calling to a UK Landline Calling to a UK Mobile
£10, £25, £50 £0.015/min (1.5p) £0.055/min (5.5p)

Top up call credit on your account only when you need to.
Set up Automatic Top Up to manage this for you.

Pay Monthly

Tariffs Calling to a UK Landline
(UK Landline minutes)
Calling to a UK Mobile
(UK Mobile minutes)
£10 per month 680
£0.015/min (1.5p)
£0.05/min (5p)
£15 per month 1,080
£0.014/min (1.4p)
£0.047/min (4.7p)
£25 per month 1,950
£0.013/min (1.3p)
£0.045/min (4.5p)
£45 per month 3,800
£0.012/min (1.2p)
£0.043/min (4.3p)
£60 per month 5,500
£0.011/min (1.1p)
£0.04/min (4p)

Adds call credit to your account on the 1st of each month.
Buy more PAYG call credit to get extra minutes at the same rate.

The rates shown are per minute and based on calling a UK destination. A minimum cost of £0.015 (1.5p) applies to each chargeable call.

For all other destinations, please download our rate sheet.

Download Rate Sheet

SIP Trunks FAQ's

  • What do I need to get started?

    expandable icon

    An Internet connection (3G, 4G, broadband)

    A Virtual Number from TTNC

    An IP PBX

  • How much bandwidth do I need?

    expandable icon

    On average, 3 concurrent calls would take about 256kbs of bandwidth when using the G.711a Codec, which is a high quality Codec TTNC uses

  • What Codec does TTNC use?

    expandable icon

    TTNC uses the G.711a Codec, which is one of the highest quality Codecs available. It provides digital quality and sound quality is superior to analog.

  • What is a Codec?

    expandable icon

    Codec stands for Coder-decoder. It converts an audio signal (your voice) into a compressed digital format for transmission (VoIP) and then back into an uncompressed audio signal for replay.

    Codecs vary in the sound quality and the bandwidth required, most softphones, IP phones, IP PBX’s and Gateways supports several different Codecs.

  • Can I use my existing number?

    expandable icon

    Yes you can. We can port almost any existing UK telephone number from any supplier onto our SIP Trunking service.

    Please contact us for more information or see our Number Porting page.

  • What kind of Internet connection do I need?

    expandable icon

    A standard broadband connection is sufficient to surf the Internet and use for voice calls at the same time.

  • What is call quality like?

    expandable icon

    Assuming you have a good Internet connection, call quality will be superior or the same as you receive when you use a landline or mobile phone.

  • Do SIP Trunks have a contract or set up charge?

    expandable icon

    No, there's no set up charge or contract to sign.

  • Can SIP Trunking replace ISDN lines?

    expandable icon

    Yes. SIP trunking provides a highly flexible alternative to ISDN and and is also more cost effective than ISDN.

  • How do SIP Trunks work?

    expandable icon

    SIP Trunks connect your PBX to TTNC's network, enabling full PSTN conectivity.

    Connection from your PBX to our network is via an IP connection, such as broadband or Ethernet, and is delivered as an end-to-end service. There's no outbound channel limit and you can add inbound channels in real time via myTTNC.

  • What are SIP Trunks?

    expandable icon

    SIP Trunks (or SIP Trunking or VoIP Trunks) enable you to use an Internet connection to make and receive calls.

For more FAQ's please visit our FAQ's page

Ordering and adding SIP Trunks

If you already have an account with TTNC and want to make use of this service from today, you can simply add this, along with any of our other services, at any time through the store in myTTNC.

Otherwise, click the button below and you'll be up and running in minutes.

Add to basket

SIP Trunks Help and User guides Download the VoIP Services PDF