SIP trunking uses the Session Initiation Protocol (SIP) as a communication protocol to establish VoIP connectivity between on-premises phones and public switched telephone networks.

What is the difference between SIP trunking and VoIP?

A VoIP trunk is only capable of transferring voice data over the internet, while a SIP trunk is capable of transporting any type of multimedia data, including voice, text, and video.

Unified Communications

SIP Trunks

Flexible, scalable SIP connectivity to modernise your existing phone system at your own pace.

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Part of Unified Communications

Modernise your phone system at your pace.

Flexible, scalable SIP connectivity that breathes new life into your existing PBX — cut line rental, add capacity instantly and keep your numbers as you move to the cloud.

Lower call costs

Replace expensive ISDN lines with cost-effective SIP and slash your line rental.

Instant scalability

Add or remove channels on demand to match seasonal or business change.

Number continuity

Keep your existing numbers and port new ones in from anywhere in the UK.

Save up to 50% on calls

Cheaper call rates than standard fixed-line services, with free site-to-site calling.

Inclusive UK minutes

Bundled UK local, national and mobile minutes included on longer contract terms.

70% off line rental

Cut line rental by up to 70% moving from ISDN to SIP, with built-in QoS to protect call quality.

Pricing

SIP Trunk price plans

SIP Trunk Basic

£5.00 per trunk / month

Unlimited inbound calls
Outbound calls from 1.5p per minute
£25.00 set-up fee per trunk
Minimum 4 SIP trunks required

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SIP Trunk All Inclusive

£8.00 per trunk / month

Unlimited inbound calls
5,000 mins/month to 01, 02 & 03 numbers
2,000 mins/month to UK mobiles
£85.00 set-up fee per endpoint

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Why businesses choose Stream

One trusted partner

From connectivity to communications, security and cloud — one team that knows your business.

24/7/365 UK support

Real experts on our own monitored network, on hand whenever you need them.

Carrier-grade & accredited

Built on infrastructure accredited to ISO 9001 and ISO 27001 for peace of mind.

FAQs

SIP Trunks, answered

What is a SIP trunk?

SIP trunking uses the Session Initiation Protocol (SIP) to establish VoIP connectivity between your on-premises phone system and the public telephone network, replacing traditional ISDN lines.

What's the difference between SIP trunking and VoIP?

VoIP only carries voice data over the internet. A SIP trunk can carry any type of multimedia data — voice, text and video — over the same connection.

How quickly can SIP trunks be set up?

Additional voice channels can be added to your existing PBX within hours of ordering — compare that to up to 30 days for a traditional ISDN30 install.

Do I need to replace my existing phone system?

No — SIP trunks connect to your existing PBX, letting you modernise your connectivity and cut costs without replacing your phone system.

Explore our other communications products

Ready to talk about SIP Trunks?

Our team will help you scope the right solution for your business — with support that's always on.

Talk to our team 01635 884 170