By the time you have shortlisted a few SIP trunk providers, the easy part is over. Each has a decent website, a friendly sales contact and a quote. The differences are real, but they are spread across contract terms, support promises and technical details that are hard to line up side by side.
A simple weighted scorecard fixes that. It turns a vague feeling (“Provider B seems better”) into something you can explain and defend. This guide gives you a scorecard built for UK businesses, explains what evidence to ask for under each heading, and shows how it plays out in practice.
Why a Scorecard Beats a Price Comparison
Price is the easiest thing to compare, so it tends to dominate. Searching for the cheapest UK VoIP providers will always surface low headline rates. But a low rate can come with a long minimum term, thin support or a fee to port your numbers out.
A scorecard forces you to decide, before you see the quotes, what matters most. That protects you from being swayed by whichever salesperson was most persuasive, and it gives your team a shared basis for the decision.
The Scorecard: Criteria and Suggested Weights
The weights below total 100. Adjust them to suit your business. A contact centre might push resilience higher, while a small office might care more about migration help.
| Criterion | Suggested weight | What to look for |
|---|---|---|
| Resilience and failover | 20 | Multiple data centres, automatic rerouting, clear fault history |
| Number porting and migration support | 15 | Written timelines, named contact, plan for delays |
| Support and fault response | 15 | Response and fix targets, out-of-hours cover, UK-based staff |
| Total cost, itemised | 15 | Channels, calls, numbers, setup, exit fees |
| Contract flexibility and exit | 10 | Term length, notice period, exit for persistent failure |
| Security and fraud controls | 10 | Spend limits, alerts, fraud monitoring, liability terms |
| Compatibility and integration | 10 | PBX support, Teams integration, cloud PBX options |
| Portal and reporting | 5 | Self-service changes, readable call records |
Score each provider from 0 to 5 on each row. Multiply the score by the weight, divide by 5, and add up the results. The total is out of 100.
What Evidence to Ask For
A score is only as good as the information behind it. For each criterion, ask for something concrete.
Resilience and failover
Ask where the platform runs, how traffic is rerouted if one site fails, and what options exist if your own connection drops. A confident provider will explain this simply. Vague talk of “enterprise-grade reliability” earns a low score.
Number porting and migration
Request a written timeline and the name of the person handling your port. Ask what happens to your charges if the provider causes a delay. Porting is where many migrations stall, so this deserves its weighting.
Support and fault response
Look for separate targets for acknowledging and resolving faults, and check whether they apply outside office hours. A firm that takes evening orders cannot rely on a weekday-only help desk.
Total cost
Ask for itemised pricing, then rebuild it against a real month of your call data. Include calls to mobiles, number rental and any fees on exit. Score the lowest total highest, not the lowest channel price.
Contract and exit
Check the minimum term, the notice period and whether you can leave without penalty after repeated service failure. Confirm that your numbers can be ported out and whether that costs anything.
Security and fraud
Toll fraud can generate large bills quickly if a phone system is compromised. Look for spend limits, alerts and clear wording on who is liable.
Compatibility
Confirm that your PBX supports SIP, or what a gateway would cost. If you use Microsoft Teams or plan to move to hosted telephony later, ask how the provider supports that.
Portal and reporting
A good call management portal lets you change routing and view call records without raising a ticket. This carries a lower weight, but it affects daily life.
A Worked Example
The scores below are purely illustrative, to show the method.
A 30-person professional services firm in the North West is replacing ISDN lines and keeping its existing PBX. It shortlists two UK SIP trunk providers.
Provider A scores well on porting (5), compatibility (5), support (4), resilience (4), contract (4) and security (4). It scores 3 on cost and 3 on portal quality. Weighted total: 81.
Provider B is cheaper and more resilient, scoring 5 on both cost and resilience. But it scores only 3 on porting, 3 on support, 3 on security and 2 on contract flexibility, because of a 36-month term and a fee to port numbers out. It scores 4 on compatibility and portal. Weighted total: 75.
Provider B looked better on price and infrastructure. The scorecard shows why Provider A still comes out ahead: a smoother migration, clearer exit terms and stronger support matter more to this firm. A different business might weight things differently and choose B.
Tips for Scoring Fairly
A few habits keep the process honest.
- Set weights first. Agree them with colleagues before reading any quotes.
- Score as a group. Have two or three people score independently, then compare. Large gaps reveal what needs discussion.
- Use evidence, not impressions. If a provider cannot give a written answer, score it low.
- Ask every provider the same questions. Otherwise you are comparing different conversations.
- Run a small trial. A few test channels can reveal call quality and support responsiveness before you commit fully.
- Add a pass/fail gate. Some items, such as 999 and 112 emergency calling or number portability, should be non-negotiable regardless of score.
Do Not Forget Your Own Side
Even the best SIP provider in the UK cannot make up for a weak local network. Check that your broadband or leased line can handle peak call volumes, that your router and firewall are SIP-friendly, and that your PBX is supported. Time also matters. Openreach is retiring the copper-based phone network, with the current deadline set for January 2027, so providers are likely to get busier as the date approaches, and good installation slots will be harder to secure.
Providers such as Wavetel Business, which works with UK organisations on VoIP and business communications, should be comfortable answering scorecard-style questions in writing. How a provider handles that request is itself useful evidence.
Frequently Asked Questions
What is the most important factor when choosing a SIP trunk provider?
It depends on your business, but resilience, number porting and support usually matter more than a small saving on channel price. Weight them according to what a missed call costs you.
How many providers should I shortlist?
Two or three is usually enough. More than that and the comparison becomes unwieldy without improving the decision.
Should I choose the cheapest option?
Not by default. Compare total cost over the contract term, including call charges, setup and exit fees, and then weigh it against service quality.
Can I use the same scorecard for hosted telephony?
Mostly, yes. Add criteria for handsets, user licences and integrations, and reduce the weight on PBX compatibility.
What if two providers score almost the same?
Run a short trial, speak to existing customers, or check how each handles a specific question you care about. Small differences in service often show up quickly.
Conclusion
Choosing between SIP trunk providers is easier when you decide what matters before you see the quotes. A weighted scorecard gives you a clear method: set weights, ask for evidence, score each provider and compare totals.
Your practical next step: copy the criteria above into a spreadsheet, adjust the weights to suit your business, and send the same set of questions to each shortlisted provider. The answers, and how clearly they are given, will tell you more than any brochure.
