PBX to VoIP Migration Checklist: A Step-by-Step Plan for 2026

A PBX to VoIP migration goes wrong in the details, not the big decisions. The provider you pick matters, but so does whether you remembered the fax line, updated your 911 address, or tested the auto attendant before customers started calling it. This checklist turns a PBX replacement into a phased plan you can actually execute, from your first audit through the week after cutover.

For the reasoning behind each phase, our PBX to VoIP migration guide covers the why. This is the checklist to work from once you are ready to move. And if you are still building the case for the switch internally, 10 advantages of PBX to VoIP lays out what you stand to gain.

Phase 1: Pre-Migration Audit

Before you talk to a single provider, know exactly what you are replacing. Skipping this step is the single biggest reason PBX migrations run into surprises later, because you cannot plan around a line, integration, or device you never wrote down.

• [ ] Inventory every extension, line, and device on your current PBX
• [ ] Map your call flows: who answers, where calls route, what happens after hours
• [ ] List every system your phone setup touches, including your CRM, scheduling tool, and helpdesk
• [ ] Note any analog lines that are easy to forget, like fax machines, alarm panels, elevator phones, and overhead paging
• [ ] Record your current call volume and peak-call times
• [ ] Confirm the account holder name and billing address on file with your current carrier
• [ ] Check your current contract for an end date or early termination terms
• [ ] Name one person to own the migration from start to finish

Phase 2: Choose Your Provider

Not every VoIP implementation is built the same way, and the provider you choose here shapes how smooth the rest of this checklist goes. Vet providers on more than price, since the cheapest quote is rarely the cheapest system once add-ons and fees are added back in.

• [ ] Confirm AI answering is included in the plan, not a paid add-on
• [ ] Confirm pricing is billed by the second, not rounded up to the nearest minute
• [ ] Ask how the provider handles network reliability and outages
• [ ] Confirm compatibility with your CRM and other integrations
• [ ] Get a clear answer on what onboarding and number porting support is included
• [ ] Ask what happens if you need to add or remove users later
• [ ] Read the contract terms closely, and confirm there is no long-term lock-in

If you want the full list of questions to ask before you sign anything, see 10 questions to ask potential VoIP providers.

Phase 3: Prep Your Network

VoIP call quality depends on your network being ready before go-live, not after.

• [ ] Run a bandwidth check and confirm headroom above your normal data traffic
• [ ] Set up Quality of Service (QoS) so voice traffic is prioritized
• [ ] Confirm wired connections at desks with heavy call volume
• [ ] Verify Power over Ethernet (PoE) switches are in place if you are keeping desk phones
• [ ] Confirm a backup connection or mobile failover plan in case your primary internet drops
• [ ] Review firewall and security settings for VoIP traffic

Phase 4: Port Your Numbers

Number porting is usually the slowest part of a migration, so start it early and do not cancel anything until it is confirmed.

• [ ] Submit your port request through your new provider
• [ ] Double-check the account holder name and billing address match your old carrier's records exactly
• [ ] Keep your existing service active until the port is fully confirmed
• [ ] Update your E911 address in the new system
• [ ] Set a target port date with buffer room in case of delays
• [ ] Notify staff of the target date so nobody is surprised by a brief change in call behavior

Phase 5: Schedule Cutover Day

A cutover plan is what separates a smooth switch from a disruptive one. Everything in the phases above exists to make this day boring, and boring is exactly what you want when your phone system changes underneath a working business.

• [ ] Pick a low-traffic window, like a weekend or the start of a slow day
• [ ] Assign one person to own cutover day and watch for issues in real time
• [ ] Test inbound and outbound call flows before flipping over
• [ ] Test your auto attendant or AI voice agent greeting and routing
• [ ] Confirm voicemail and call forwarding work as expected
• [ ] Prepare a rollback plan in case something needs to revert
• [ ] Notify staff, and any key customers or vendors who call your main line, of the change

Phase 6: Cutover Day

• [ ] Confirm the number port has completed
• [ ] Place live test calls on the new system
• [ ] Verify caller ID displays correctly on outbound calls
• [ ] Confirm integrations are syncing call data to your CRM or helpdesk
• [ ] Verify your E911 address is correct with your new provider
• [ ] Decommission or repurpose old PBX hardware
• [ ] Watch call volume and quality closely for the first few hours

Phase 7: Week One Validation

The first week is when small issues surface. A cutover can look flawless on day one and still have a misrouted extension or a broken sync that nobody notices until a customer mentions it, so do not skip this step.

• [ ] Review call logs for missed or misrouted calls
• [ ] Confirm voicemail-to-email or transcription is working
• [ ] Check that integration records are updating correctly
• [ ] Collect staff feedback on any rough edges with the new system
• [ ] Confirm after-hours and AI answering behave as expected
• [ ] Close out your old carrier account only after everything checks out

Common Mistakes This Checklist Prevents

Most PBX migration problems trace back to a step that got skipped, not a step that went wrong. Forgotten analog lines, integrations left disconnected, and untrained staff cause more disruption than the actual phone switch does. For a deeper look at what tends to break and why, see the what breaks during a migration section of our full guide.

How CallSprout Supports Your Migration

CallSprout walks through this checklist with you instead of handing it over and disappearing. We help with the audit, the provider comparison, the port, and the cutover itself, and we stay involved through week one.

Every plan includes Sage, our AI voice agent, so you are not migrating to a phone system that still sends after-hours calls to voicemail. Pricing is one transparent plan with no contract, billed by the second. Plans start at $22.95 per user per month. Explore the CallSprout platform or check the pricing page for the full breakdown.

Frequently Asked Questions

Is this checklist enough to complete a full VoIP implementation on my own?

For most small businesses, yes, especially with a provider that supports you through porting and cutover. Larger or multi-location businesses may want a dedicated project owner internally, but the phases here cover what a complete implementation needs.

What is the difference between a PBX replacement and a partial upgrade?

A PBX replacement moves your phone system entirely to the cloud, including call routing, voicemail, and any AI answering. A partial upgrade might add features like texting or call recording on top of your existing PBX without replacing the core hardware. This checklist assumes a full replacement.

How far in advance should I start working through this checklist?

Start with the pre-migration audit as soon as you are seriously considering a switch, well before you pick a cutover date. Number porting in particular depends on your current carrier's process, so the earlier you start Phase 4, the more buffer you have if anything takes longer than expected.

Ready to Check Off Your Migration?

Ready to leave your PBX behind? Contact us to start your migration plan, or see our pricing to find out what the switch costs for your team.