PBX to VoIP Migration: Costs, Checklist, and Number Porting Guide
Moving off a PBX comes down to three practical questions: what it will cost, whether you can keep your phone numbers, and how to avoid a day when customers can't reach you. This guide answers all three for US small and mid-sized businesses, using FCC rules and published pricing instead of round-number guesses.
Key takeaways
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What a PBX to VoIP Migration Involves
A PBX to VoIP migration replaces an on-premises phone switch and its carrier lines with a system that sends calls over your internet connection. Your numbers, extensions, menus, and voicemail are rebuilt in the new platform, and staff answer on IP desk phones, a browser, or a mobile app.
Not every business should replace the PBX. If the equipment is modern and stable, adding SIP trunking in place of old carrier lines can be enough.
Your situation | Better fit |
PBX is old, unsupported, or hard to repair | Full cloud migration |
PBX is recent and works; the problem is costly phone lines | Keep the PBX, add SIP trunking |
Staff work remotely or across several sites | Full cloud migration |
You want no call-control hardware on site | Full cloud migration |
Heavy use of fax, paging, or alarm lines | Either, with adapters budgeted |
If you are leaning toward the full move, a cloud-based business phone system removes the on-site hardware entirely. Our guide to the VoIP PBX phone system explains how the pieces fit together.
What Does PBX to VoIP Migration Cost?
The monthly plan is the smallest part of the picture. Budget for these lines:
Cost item | When | How to estimate |
Platform fee | Monthly | Provider's published per-user price |
Carrier usage | Monthly | Call minutes and numbers, metered or bundled |
Phones and headsets | One-time | Only for desk phones that are not SIP-compatible |
Network upgrades | One-time | Router with QoS, PoE switches, backup connection |
Porting fees | One-time | Ask both carriers; the FCC notes companies may charge to port a number |
Setup and training | One-time | Staff hours plus any provider setup fee |
Old PBX overlap | Short-term | Lines and maintenance continue until the port is confirmed |
Example: Estimate the Monthly Platform Cost
Using SwitchBoard Cloud’s published pricing as an example, teams of up to five users pay $125 per month, while teams of 6 to 15 pay $25 per user per month. A 10-person office would therefore pay $250 per month for the platform, before call usage.
System setup, IVR setup, and the web phone app are included. SwitchBoard Cloud runs on a Twilio account that the customer owns, so call usage is billed separately by Twilio. The account requires a $20 minimum starting balance. Include both the platform fee and usage when comparing options.
Review the current details on the SwitchBoard Cloud pricing page.
Calculate Your Current Baseline
Add up 12 months of current phone expenses, including carrier lines or PRI rental, maintenance contracts, long-distance charges, and repairs. Divide that total by 12, then divide by the number of users. Compare this baseline with the full cost of the proposed system. Savings depend on your current contracts, usage, equipment, and support needs, so use your invoices rather than relying on a general savings percentage.
PBX to VoIP Migration Checklist
Migrating from a traditional PBX to VoIP involves more than replacing your phone system. Use this quick checklist to track the essential tasks before, during, and after migration.
Quick PBX to VoIP Migration Checklist
Inventory numbers and devices: List all business numbers, extensions, phones, and connected equipment.
Map existing call flows: Document business hours, IVR menus, transfers, and voicemail routing.
Assess network readiness: Check bandwidth, internet stability, QoS, and PoE requirements.
Choose a migration approach: Decide between a phased rollout and an all-at-once cutover.
Verify provider compatibility: Confirm supported phones, features, pricing, and migration assistance.
Prepare number porting: Gather carrier account details and required authorization documents.
Configure and test VoIP: Test inbound and outbound calls, routing, voicemail, and call quality.
Complete cutover and monitor: Verify number transfers, monitor performance, and cancel legacy services only when safe.
1. Inventory Every Number and Device
List every main, direct, toll-free, and fax number, along with each extension and device. Compare the list with your carrier invoice. Older systems may also have fax machines, alarm panels, door phones, or overhead paging systems that need analog adapters or another solution.
2. Map Your Call Flows
Document what happens when someone calls the main number during business hours, after hours, on holidays, and when nobody answers. Identify the menus, ring groups, transfers, and voicemail paths that staff still use. Remove outdated options instead of automatically copying the old setup.
3. Check Your Network
A common planning estimate is about 100 kbps per simultaneous call. Check peak concurrent calls in your PBX logs, confirm that your router can prioritize voice traffic through QoS, and plan for Power over Ethernet (PoE) switches if you will keep desk phones. Wired connections are generally preferable for busy desks.
4. Choose a Phased or All-at-Once Cutover
Small offices may be able to switch over during a single weekend. Multi-location businesses often reduce risk by migrating one team or site at a time.
5. Evaluate Providers and Phone Compatibility
Compare providers against your call-flow requirements. Ask who handles porting paperwork, what service-level commitment is provided in writing, and whether your current phones will work.
Check VoIP phone compatibility before purchasing replacement devices.
6. Start Porting Paperwork Early
Gather account details and authorization documents early, since collecting accurate information can take longer than expected. Do not schedule the number transfer until the new system is configured and tested.
7. Build and Test Before Cutover
Create users, business hours, voicemail, menus, and queues. Place inbound test calls from mobile and landline numbers. Try every menu option, after-hours route, transfer, and voicemail path. Confirm that messages are delivered as expected.
Take extra care when configuring IVR and call routing. Call menus and routing are often the first parts of the system callers experience.
8. Cut Over and Monitor
Choose a low-traffic window for the switch. Retest immediately after cutover, then monitor call quality and missed calls for two weeks. Cancel the old service only after every important call path has been confirmed.
Number Porting Guide for US Businesses
Porting moves your existing numbers from your current carrier to the new provider. The FCC says customers can generally keep their number when staying in the same geographic area, and that a new provider can start the process for you. Some rural carriers hold waivers, so check early if you are in a small market.
Port type | FCC interval | Typical case |
Simple | One business day | Generally a single line without complex switch changes |
Non-simple | Four business days | Generally multiple lines or PBX number blocks |
Large project | Provider-specific | Twilio: 4 to 6 weeks for 50+ numbers |
Most PBX ports involve several numbers, so do not plan around the one-day figure. Rejections add the most time. Twilio says the most common reason for rejection is incorrect name or address information.
Gather Before You Submit:
Current carrier name and account number
Billing telephone number and any account PIN
Authorized name and service address exactly as the carrier has them
A signed Letter of Authorization
A recent bill, dated within the last 30 days
Three Rules That Prevent Most Port Problems:
Do not cancel service or disconnect numbers. Twilio notes a disconnected number causes the port to fail.
Make your name and address match the carrier's records, even if that looks outdated.
Confirm your 911 address afterward. FCC rules under Kari's Law and RAY BAUM'S Act cover direct 911 dialing, notification, and dispatchable location for multi-line systems, including IP-based ones.
If you text from ported local numbers, ask your provider about messaging registration, since Twilio requires approved A2P 10DLC registration for messaging on ported US local numbers.
Mistakes That Cost the Most Time
Even a well-planned migration can face delays if important details are overlooked. Avoid these common mistakes:
Treating the port date as the project deadline: Porting requests can be delayed. Complete system setup and testing before the confirmed transfer date.
Copying outdated phone menus: Review existing IVR menus, extensions, and call routes instead of transferring unnecessary options.
Overlooking network readiness: Insufficient bandwidth or unstable internet can cause dropped calls and poor audio quality.
Assuming all existing phones are compatible: Check SIP compatibility and device requirements before migrating.
Forgetting carrier account details: Missing account numbers, PINs, or authorization documents can delay number porting.
Canceling old service too early: Keep your existing phone service active until number transfers and call routing are verified.
Ignoring connected analog devices: Fax machines, alarm systems, and paging equipment may require adapters or alternative connections.
Skipping employee training: Briefly train staff on transfers, voicemail, call handling, and web phones before cutover.
Missing compliance checks: Verify emergency calling locations, call recording consent requirements, and data retention policies.
How to Avoid Downtime
Downtime usually comes from skipping rehearsal, not from VoIP itself. Three habits help:
Overlap the systems. Keep the PBX live until the port is confirmed. You pay for both briefly, and that cost is cheap insurance.
Run a pilot. Move IT or a small office team first and let them find problems.
Write the rollback in advance. Decide who can forward the main number to a mobile or answering group, and what failure triggers it. For example: main-line calls not reaching the right queue 30 minutes after cutover.
How SwitchBoard Cloud Simplifies PBX to VoIP Migration
SwitchBoard Cloud is a cloud PBX and VoIP phone system built on Twilio. It includes IVR, call queues, call recording, a browser-based web phone, and SIP phone compatibility, with setup handled by the SwitchBoard team. A 30-day free trial for up to five users lets you test your real call flows before you commit.
Know the tradeoffs. You create and fund your own Twilio account, which keeps your numbers and costs under your control but means two bills. Calls are recorded by default, so confirm your state's consent rules and turn recording off where it does not belong. It fits small and mid-sized teams that want a simple dashboard. Larger or highly customized environments should ask about volume pricing first.
Ready to Move From PBX to VoIP?
Simplify your business phone system migration with SwitchBoard Cloud. Start your 30-day free trial today and explore a more flexible way to manage business communications.
Frequently Asked Questions
What is the difference between PBX and VoIP?
PBX is a business phone system that manages internal and external calls, while VoIP is a technology that transmits voice calls over the internet. Traditional PBX systems typically use dedicated telephone infrastructure, whereas cloud PBX solutions use VoIP to provide calling features without requiring an on-site PBX server.
Can a business use VoIP with its existing internet connection?
Yes, most business internet connections can support VoIP if they offer sufficient bandwidth, low latency, and stable connectivity. However, businesses with high call volumes should assess network capacity, configure Quality of Service (QoS), and consider backup connectivity to maintain reliable call quality.
What happens to fax machines when switching to VoIP?
Traditional fax machines may not work reliably over standard VoIP connections. Businesses can consider online fax services, compatible analog telephone adapters, or fax solutions supporting the T.38 protocol. The right option depends on existing equipment, document volume, and provider compatibility.
Is SIP trunking the same as cloud PBX?
No. SIP trunking connects an existing PBX system to telephone services over the internet, allowing businesses to retain compatible on-premises equipment. Cloud PBX moves phone system management to a hosted platform, reducing the need to maintain physical PBX hardware.
Can employees use VoIP phones while working remotely?
Yes. Cloud-based VoIP systems can allow employees to make and receive business calls through supported desk phones, desktop applications, or mobile softphones. This helps businesses maintain consistent call handling across office, home, and hybrid work environments.
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