- Openreach is retiring the public switched telephone network and moving every line onto all-IP technology, a programme due to complete in 2027.
- Ofcom oversees number portability rules in the UK, so a business can generally keep its existing phone numbers when moving from analogue to a VoIP provider.
- VoIP runs over a broadband connection, so the suitability of the office internet line is the first thing to confirm during a migration audit.
- Geographic numbers beginning 01 and 02, and 03 numbers, can typically be ported to a hosted VoIP platform under Ofcom number portability arrangements.
- Because the analogue network is being withdrawn, small businesses that take no action risk losing service on legacy lines as their area is migrated.
Start with an audit of lines, numbers and broadband, then choose a provider, port your numbers, test thoroughly and train staff before going live, all well ahead of the 2027 all-IP deadline.
Last reviewed: June 2026
Why the 2027 deadline matters for small firms
The analogue telephone network that has carried business calls for decades is being switched off. Openreach is migrating all lines to digital, all-IP services, with the programme scheduled to complete in 2027. For a small business, that is not an optional upgrade but a change that will reach every line eventually. The mechanism is gradual rather than a single national switch: Openreach moves exchange areas in batches, and once an area is migrated, new analogue and ISDN provisioning stops and existing lines are converted to all-IP equivalents. Acting early turns a forced cutover into a planned project with time to test and adjust.
Leaving the move until the last moment carries real risks. Provider lead times, number porting windows and the need to retrain staff all take time, and they compress badly if a migration is rushed in the final weeks before a local switch-off. There is also a practical capacity point: as the programme nears completion, many firms will be migrating at once, and provider and installer availability tends to tighten under that demand. A staged approach, started well in advance, spreads the work and reduces the chance of a gap in service when it matters most. It also leaves room to absorb the inevitable small problems, such as a number port that needs a corrected line record or a feature that behaves differently on the new platform, without those problems turning into customer-facing outages.
Step one: audit what you have
Every migration should begin with a clear picture of the current setup. List every phone line, including any used for alarms, card payment terminals, door entry systems or lift lines, because these often sit on analogue circuits that staff forget about. Lift emergency telephones in particular are governed by the BS EN 81-28 standard, which requires a reliable two-way voice link to a rescue service, so any lift line on the analogue network needs a deliberate replacement plan rather than an assumption that it will simply keep working. Record each phone number, who uses it and whether it is advertised to customers, since published numbers must be preserved through the move. Note the existing call volumes and any features in use, such as call queues, voicemail or call recording.
The broadband line deserves particular attention. VoIP carries calls as data, so the office connection needs enough capacity and stability to handle simultaneous calls alongside normal internet use. A rough rule is to allow a modest, steady slice of bandwidth for each concurrent call and to check the upload speed rather than only the headline download figure, because call audio travels in both directions. An audit should confirm the connection type and whether it is fit for purpose, or whether a broadband upgrade should run alongside the voice migration. It is also worth recording whether the line is fibre-to-the-premises, a cabinet-based service or an older copper product, as that affects both the resilience of the connection and what upgrade options exist. Documenting all of this creates the baseline that the rest of the project is measured against.
SME VoIP migration project plan
The table below sets out a typical phased plan for a small business. Timings are indicative and will vary with the number of lines and the complexity of the existing system, but the sequence holds in most cases.
| Phase | Main activity | Who is involved |
|---|---|---|
| Audit | List lines, numbers, features and broadband | Owner, office manager, IT |
| Select provider | Compare features, capacity and support | Owner, IT or adviser |
| Port numbers | Submit porting request, agree cutover date | New provider, losing provider |
| Test | Check calls, features, audio quality | IT, sample of staff |
| Train and go live | Brief staff, switch over, monitor | All staff, IT, provider |
Step two: choose a provider
With the audit complete, a business can match its needs against what providers offer. The features identified in the audit, such as call queues, voicemail to email, call recording where lawful, and the number of simultaneous calls, form a requirements list to assess each option against. Where call recording is in scope, it brings data-protection obligations under UK GDPR and the Data Protection Act 2018, so the business should be clear on why recordings are kept, how long they are retained and how callers are informed. Support arrangements matter too, particularly for a small firm without dedicated IT, so the level and hours of help available during and after the move are worth checking.
Contract terms and the migration support a provider offers should be considered alongside the headline features. Some providers handle number porting and configuration on the customer's behalf, which reduces the load on a small team, while others supply the platform and leave the setup to the customer or a third-party installer. It is also sensible to confirm what happens at the end of the contract, whether the numbers remain portable to another provider later and whether handsets are tied to the platform. The aim at this stage is not to chase the cheapest line but to select an option that covers the documented requirements and provides a clear, supported path through the cutover.
Step three: port numbers, test and train
Keeping existing numbers is usually the priority, and Ofcom number portability arrangements generally allow geographic 01 and 02 numbers, and 03 numbers, to move to a hosted VoIP platform. Porting is requested through the new provider, who coordinates with the current provider and agrees a cutover date. It is important not to cancel the old line before the port completes, because cancelling first can cause the number to be lost. Accurate details on the porting request matter as well: the number, the account or line identifier and the installation address need to match the records the losing provider holds, because a mismatch is one of the most common reasons a port is rejected and delayed. The new provider should confirm the porting window and any details needed to avoid a gap.
Testing comes before any wide rollout. The team should confirm that inbound and outbound calls work, that ported numbers ring through correctly, that voicemail and call transfer behave as expected, and that audio quality holds under realistic load. A pilot with a small group catches problems while they are easy to fix, and it is worth deliberately testing calls to 999, to 101 and 111, and to any out-of-hours or supplier numbers the business relies on. Training then prepares the wider workforce: staff need to know how the new handsets and softphones work, how to transfer and hold calls, and who to contact if something fails. Running the migration in this order, with time built in before the 2027 deadline, gives the strongest chance of a smooth changeover.
Planning for power cuts and emergency calls
An analogue line drew a small amount of power from the exchange, so a basic corded phone kept working in a power cut. VoIP does not behave that way: if the office loses mains power or the broadband connection drops, the handsets and the router lose power too, and calls including 999 will not connect unless a backup is in place. Ofcom expects providers to offer at least one solution that allows an uninterrupted means of contacting the emergency services for a reasonable period during a power outage, but the business still has to plan around the limits of that arrangement, particularly where staff or customers may be vulnerable.
Practical resilience for a small firm usually combines a few measures. An uninterruptible power supply can keep the router and key handsets running through a short outage, while a mobile-based fallback gives a route for emergency and customer calls if the broadband itself fails. Numbers can also be set to divert automatically to a mobile or to another site when the primary connection is unreachable, so callers are not met with silence. Documenting which lines are business-critical during the audit makes this planning far simpler, because the resilience effort can then be concentrated where an outage would do the most harm rather than spread thinly across every extension.
Frequently Asked Questions
Where do I start with migrating to VoIP for my business?
Start with an audit. List every phone line, including those used for alarms, lift lines or card terminals, record all numbers and the features in use, and check whether the broadband connection can support voice calls. This baseline tells you what the new system must replicate, whether a broadband upgrade is needed alongside the voice move, and which lines are critical enough to need resilience planning.
How long does a small business VoIP migration take?
It varies with the number of lines and the complexity of the existing system, so a precise duration cannot be promised. The main time drivers are provider lead times, the number porting window and staff training. Starting well ahead of the 2027 all-IP deadline gives room to test and adjust rather than rushing a last-minute cutover, and it avoids the capacity squeeze likely as more firms migrate near the end of the programme.
Can I keep my business phone numbers when moving to VoIP?
In most cases yes. Ofcom number portability arrangements generally allow geographic 01 and 02 numbers, and 03 numbers, to be ported to a hosted VoIP platform. The new provider coordinates the port with your current provider. Do not cancel the existing line before the port completes, as that can cause the number to be lost, and make sure the account and address details on the request match the losing provider's records to avoid a rejection.
What should I test before going live on VoIP?
Confirm that inbound and outbound calls connect, that ported numbers ring through correctly, and that features such as voicemail and call transfer work as expected. Check audio quality under realistic call load, ideally with a small pilot group, and test emergency and key supplier numbers, so any problems are found and fixed before the wider rollout.
Who helps businesses migrate to VoIP?
VoIP providers and IT support partners commonly handle migrations, including number porting and configuration. Some providers run the porting and setup on the customer's behalf, which helps small firms without dedicated IT. The right level of support is something to confirm when choosing a provider, especially the help available during and after the cutover.
