Disclosure: This post contains affiliate links. If you click and purchase, I may earn a commission at no extra cost to you.
Last Updated: August 14, 2026
Switching from a legacy phone system to VoIP can cut a small business’s monthly phone bill by 40–60% — but only if the migration is done in the right order. This guide walks through every prerequisite, decision point, and configuration step a small or mid-sized business needs to complete before, during, and after a VoIP migration. Skip the network prep and you’ll get choppy calls. Skip the compliance check and you’ll get a regulatory headache. Follow the sequence below and you’ll have a working, cost-effective VoIP system without the war stories. For more details, see our guide on how much you can actually save switching from legacy systems. For more details, see our guide on VoIP requirements for distributed and remote teams. For more details, see our guide on finding VoIP providers with local support and compliance expertise. For more details, see our guide on industry-specific VoIP solutions for contractors and service businesses.
VoIP (Voice over Internet Protocol) is a technology that transmits voice calls as data packets over a broadband internet connection instead of traditional copper phone lines. Modern hosted VoIP platforms bundle calling, SMS, video conferencing, and CRM integration into a single monthly subscription — typically $15–$35 per user per month, compared to $50–$75 per user per month on legacy PBX or landline systems. For more details, see our guide on comparing VoIP systems side-by-side on features and pricing. For more details, see our guide on detailed comparison of RingCentral, Dialpad, and 8×8 for SMBs.
[IMAGE: alt=”VoIP phone system setup on a modern office desk with softphone interface visible on laptop” | filename=”voip-office-setup-smb.jpg”]
Why Are Small Businesses Overpaying for Phone Service Right Now?
Most of the businesses I talk to have no idea what their phone system actually costs them. They see one line on the invoice labeled “telecom” and assume it’s fixed. It isn’t.
Legacy PBX systems carry at least four cost layers that hosted VoIP eliminates: per-minute long-distance charges, hardware maintenance contracts, on-site technician fees when something breaks, and per-line rental fees that scale poorly as headcount grows. A 15-person professional services firm paying $1,100 per month on a legacy system — line rental, a maintenance contract on aging Avaya hardware, and long-distance overages — can realistically land at $420 per month after switching to a hosted VoIP platform. That’s a $680 monthly reduction, or $8,160 per year, on a 15-seat deployment. For more details, see our guide on top-rated hosted PBX providers evaluated for small business. For more details, see our guide on real cost savings examples from Florida small businesses.
The hidden cost that catches people off guard is the maintenance contract. When an on-premises PBX fails, you’re calling a specialized technician at $150–$200 per hour, often with a minimum 2-hour charge. With hosted VoIP, the provider’s infrastructure team handles that — it’s baked into the subscription.
Key takeaway: The average SMB pays $50–$75 per user per month on legacy phone infrastructure; hosted VoIP typically costs $15–$35 per user per month, and eliminates hardware maintenance and long-distance charges entirely.
What Do You Need Before You Can Switch to VoIP?
Think of this as your pre-flight checklist. Every item below needs a confirmed answer before you contact a single VoIP provider. Businesses that skip this step end up mid-migration when they discover a problem — and mid-migration is the worst time to find out your router doesn’t support QoS or that your main number can’t be ported for six weeks.
- Broadband internet with sufficient bandwidth. Minimum 100 Kbps upload and download per concurrent call. In practice, budget 1 Mbps per user to give yourself quality headroom for packet loss and jitter bursts.
- A router and managed switches that support QoS tagging. Quality of Service (QoS) prioritizes voice packets over file downloads and video streaming. Without it, a large file upload can make your calls sound like a bad AM radio signal.
- An inventory of your current phone numbers. List every Direct Inward Dial (DID) number and any toll-free numbers. You’ll need this for the porting process — missing even one number causes customer-facing disruption.
- A count of concurrent users and peak call volume. “We have 20 employees” is not the same as “we have 20 employees who all make calls at the same time.” Know your peak simultaneous call count.
- Compliance verification. Businesses in healthcare must confirm the VoIP provider will sign a HIPAA Business Associate Agreement (BAA). Finance and payment-processing businesses need PCI-DSS alignment. This is non-negotiable — not all providers offer a BAA.
- Endpoint decision. Choose between softphones (apps on laptops or mobile devices), IP desk phones, or a hybrid of both. This affects both your per-user cost and your network configuration.
- A documented baseline of current monthly telecom spend. You can’t measure ROI without a before number. Pull three months of invoices and get a real average.
[IMAGE: alt=”VoIP requirements checklist on a clipboard next to a router and IP desk phone” | filename=”voip-requirements-checklist.jpg”]
Key takeaway: Before contacting any VoIP provider, confirm your broadband bandwidth, QoS capability, number inventory, concurrent call count, compliance requirements, endpoint preference, and current telecom spend baseline.
Step 1: How Do You Audit Your Current Phone System and Network?
Start with the network, not the phone system. Most VoIP migrations that fail do so because of network problems, not platform problems. Gartner has reported that 70% of VoIP migration failures stem from inadequate network preparation rather than the platform itself — and that tracks with what practitioners see in the field.
Run an internet speed test using Speedtest.net or PingPlotter and record your upload speed, download speed, and latency. For acceptable VoIP quality, you need latency below 150 milliseconds. Above 150 ms and callers start noticing delay. Above 300 ms and conversations become genuinely difficult.
Next, log into your router’s admin interface and check whether QoS settings exist and whether they’re currently configured. Many small business routers have QoS capabilities that were never turned on. If your router has no QoS at all, that’s a hardware upgrade you need to budget before migration day.
Then pull your last three months of telecom invoices and break them into categories: line rental, long-distance charges, hardware maintenance, and support contracts. This categorization tells you exactly which cost buckets VoIP will eliminate and which might persist (fax lines, alarm system lines, elevator phones — these require separate handling via ATA adapters or dedicated analog lines and are easy to overlook).
For businesses operating across multiple physical locations, document each site separately. A distributed operation with offices in different counties may have inconsistent internet quality across locations — and the weakest link will define your worst call quality.
Free network assessment tools like PRTG Network Monitor or the SolarWinds free tier can map your current infrastructure and flag bandwidth bottlenecks before they become VoIP problems.
Key takeaway: Audit network latency (target under 150 ms), QoS configuration, and three months of telecom invoices before choosing a platform — network deficiencies discovered mid-migration are significantly more disruptive than those caught in advance.
Step 2: Which VoIP Deployment Model Fits Your Business?
There are three deployment models, and the right choice depends on your seat count, IT resources, and appetite for upfront capital expenditure.
Hosted VoIP (UCaaS — Unified Communications as a Service) means the provider manages all the infrastructure in their data centers. You pay a per-user monthly subscription. No servers on-site, automatic software updates, and disaster recovery is built into the provider’s infrastructure. This is the right starting point for most businesses under 50 seats.
On-Premises IP-PBX puts a physical server on your network that you own and maintain. You have more control over call routing and data residency, but you’re also responsible for patches, hardware failures, and upgrades. Upfront costs typically run $10,000–$50,000 depending on seat count. This model makes sense for organizations with specific data sovereignty requirements or very high call volumes that make per-user SaaS pricing uneconomical at scale.
Hybrid connects an existing on-premises PBX to a cloud SIP trunk — you keep the hardware you have but route calls over the internet instead of traditional phone lines. This is a reasonable middle step for businesses mid-transition that aren’t ready to replace physical hardware yet.
For most SMBs evaluating hosted VoIP, the major platforms to compare are RingCentral, Microsoft Teams Phone, Nextiva, Vonage Business, and 8×8. When comparing them, focus on per-user pricing, contract length (month-to-month vs. annual), included feature sets, and the quality of their mobile apps — because softphone reliability on mobile varies more than vendors admit.
Key features to confirm are included (not add-on priced): auto-attendant, call recording, voicemail-to-email, mobile softphone app, video conferencing, SMS/MMS, and CRM integration. Some providers bundle all of these; others charge separately for call recording and SMS, which can push the real per-user cost well above the advertised rate.
[IMAGE: alt=”Comparison table showing hosted VoIP vs on-premises PBX vs hybrid deployment model differences” | filename=”voip-deployment-model-comparison.jpg”]
Key takeaway: Hosted VoIP (UCaaS) is the right choice for most businesses under 50 seats — it eliminates on-site hardware, includes automatic updates, and provides built-in disaster recovery at a predictable monthly cost per user.
Step 3: How Do You Evaluate VoIP Providers Without Getting Burned?
The sales pitch for every VoIP provider sounds nearly identical. Here’s what to actually verify before signing anything.
- Uptime SLA. Require 99.99% uptime with financial penalties for downtime. A 99.9% SLA sounds close but allows 8.7 hours of downtime per year. At 99.99%, that drops to 52 minutes. For a business where phones are revenue-critical, that gap matters.
- Number porting timeline. Confirm the provider can port your existing numbers and get a realistic timeline in writing. Standard porting takes 2–4 weeks. Complex ports (toll-free numbers, numbers from certain carriers) can take longer. Plan your cutover date around this.
- Security features. Confirm end-to-end encryption using SRTP (Secure Real-time Transport Protocol) for voice and TLS (Transport Layer Security) for signaling. The NIST guidelines on VoIP security (SP 800-58) provide a solid framework for evaluating provider security claims. If you’re in healthcare, confirm the provider will sign a HIPAA BAA before you get to contract stage — not after.
- Support model. 24/7 live support vs. ticket-only is a real operational difference. If your business operates outside 9-to-5 hours, ticket-only support means a phone outage at 7 PM on a Friday stays broken until Monday morning.
- Contract terms. Month-to-month options exist across most major platforms. Avoid multi-year lock-ins unless you’ve run the platform on a pilot first and confirmed it works on your network.
- Integration compatibility. Confirm native integration with the tools your team actually uses — Microsoft 365, Google Workspace, Salesforce, QuickBooks, or whatever your CRM happens to be. “Integration available” and “integration that works reliably” are not the same thing. Check user reviews on G2 or Capterra specifically for integration reliability.
Key takeaway: Prioritize uptime SLA (99.99% minimum with financial penalties), confirmed number porting timelines, SRTP/TLS encryption, and 24/7 live support — these four criteria eliminate the majority of providers that look good on paper but fail in practice.
Step 4: How Do You Configure Your Network for VoIP Traffic?
This is the step most businesses rush. Don’t.
Configure QoS on your router and managed switches to tag VoIP packets using DSCP EF (Differentiated Services Code Point — Expedited Forwarding). This tells every device on your network to process voice packets before anything else. Without this, a team member uploading a large file to cloud storage can degrade every active call on the network simultaneously.
Create a dedicated VLAN (Virtual Local Area Network) for VoIP devices. Isolating voice traffic from general data traffic reduces jitter, simplifies troubleshooting, and adds a layer of security by preventing data-network devices from interacting directly with your phone system. Most managed switches support VLAN configuration; unmanaged switches do not — if you have unmanaged switches, that’s another pre-migration hardware item to address.
For deployments of 20 or more seats on a shared internet connection, evaluate whether a dedicated broadband circuit or an SD-WAN solution makes sense. SD-WAN can intelligently route VoIP traffic over the best available connection in real time, which is particularly useful for multi-site operations where internet quality varies by location.
Before go-live, test call quality using a VoIP-specific testing tool. VoIP-Info.org maintains a list of open-source testing utilities. Run tests during your peak business hours — not at 2 AM when the network is idle — because that’s the only way to catch congestion-related quality issues before your customers do.
[IMAGE: alt=”Network diagram showing VoIP VLAN configuration with QoS settings on a managed switch” | filename=”voip-network-vlan-qos-diagram.jpg”]
Key takeaway: Configure DSCP EF QoS tagging and a dedicated VoIP VLAN before go-live — these two network changes prevent the majority of call quality complaints that surface in the first 30 days after migration.
Step 5: How Do You Execute the Number Port and Cutover Without Downtime?
The port and cutover sequence is where most migrations create visible disruption. Here’s how to avoid it.
- Submit the Letter of Authorization (LOA) to your new VoIP provider with your complete number list. The LOA authorizes the new provider to pull your numbers from the current carrier. Missing a number at this stage means it stays with the old carrier after cutover.
- Set a firm port date that is not a Monday. Ports often complete with minor delays. A Tuesday or Wednesday port gives you a business day on either side to resolve issues without the pressure of a weekend gap.
- Configure your new VoIP system completely before the port date. Auto-attendant, call routing, voicemail, user extensions — all of it should be tested and working on temporary numbers before your real numbers transfer. Don’t configure and port simultaneously.
- Run both systems in parallel for at least 48 hours after the port completes. Keep the old system active but with calls forwarded to the new system. This gives you a fallback if something in the routing configuration doesn’t survive the port as expected.
- Confirm every number is receiving calls correctly by calling each DID from an external phone before decommissioning the old system.
- Notify your team in advance. Employees need to know their extension numbers, how to access voicemail on the new system, and how the mobile softphone app works before day one — not during their first call.
Key takeaway: Complete all VoIP system configuration on temporary numbers before your port date, run both systems in parallel for 48 hours post-port, and verify every DID externally before shutting down the legacy system.
What Are the Most Common VoIP Migration Mistakes to Avoid?
A few patterns show up repeatedly in migrations that go sideways.
Underestimating analog line dependencies. Fax machines, alarm systems, postage meters, and elevator phones often run on analog lines that aren’t visible in the main telecom invoice. Cutting those lines without providing an ATA (Analog Telephone Adapter) or a dedicated analog replacement causes immediate operational problems that are embarrassing to explain to a building manager or a security monitoring company.
Choosing a provider based on advertised price alone. The $12/user/month plan that looks great on the pricing page often excludes call recording, SMS, and after-hours support. Calculate the total cost per user with every feature your business actually needs before comparing providers.
Skipping the pilot phase. Deploy VoIP to a small group — 3 to 5 users — for 2 to 4 weeks before migrating the entire organization. This surfaces network issues, integration problems, and user experience gaps at a scale where they’re fixable without affecting the whole business.
The Center for Internet Security (CIS) also recommends treating VoIP infrastructure with the same security rigor as any other network service — VoIP fraud (toll fraud, specifically) is a real financial risk, and providers with weak authentication controls can expose businesses to unauthorized international calls that generate thousands of dollars in charges before anyone notices.
Key takeaway: The three most common VoIP migration failures are undiscovered analog line dependencies, total-cost miscalculation from feature add-ons, and skipping a pilot phase — addressing all three before migration day prevents the majority of go-live incidents.
Frequently Asked Questions About Switching to VoIP
How much bandwidth does VoIP actually require?
Each concurrent VoIP call requires approximately 100 Kbps of upload and download bandwidth using standard G.711 codec. For practical deployment, budget 1 Mbps per user to account for packet loss, retransmission, and other voice quality factors. A 20-person office with 10 peak simultaneous calls needs at minimum 1 Mbps dedicated to voice, but a 20 Mbps business broadband connection with proper QoS configured will handle this comfortably alongside normal data traffic.
Can I keep my existing phone numbers when switching to VoIP?
Yes. Number porting allows you to transfer your existing Direct Inward Dial (DID) numbers and toll-free numbers to a new VoIP provider. The process requires a Letter of Authorization (LOA) and typically takes 2–4 weeks from submission to completion. Numbers cannot be ported while under a contract dispute with your current carrier, so confirm your account is in good standing before initiating a port request.
Is VoIP reliable enough for a business that can’t afford phone downtime?
Hosted VoIP from a provider with a 99.99% uptime SLA is statistically more reliable than a single on-premises PBX, which has a single point of failure. The key risk with hosted VoIP is internet dependency — if your broadband connection goes down, so do your calls. Businesses with zero-downtime requirements should pair hosted VoIP with a 4G/5G failover connection that automatically activates if the primary circuit fails.
What’s the difference between a softphone and an IP desk phone?
A softphone is a software application installed on a laptop, desktop, or mobile device that handles VoIP calls through the device’s speakers and microphone (or a connected headset). An IP desk phone is a physical handset that connects directly to your network via Ethernet and runs VoIP natively. Softphones cost nothing beyond the subscription; IP desk phones typically run $80–$300 per unit. Most businesses use a hybrid — desk phones for office-based staff, softphone apps for remote or mobile workers.
Do I need a new phone system if I already use Microsoft Teams?
Not necessarily. Microsoft Teams Phone (formerly Teams Calling Plans) adds PSTN calling capability directly to Teams, turning it into a full VoIP phone system. If your organization already uses Microsoft 365, Teams Phone can replace a separate VoIP platform entirely — users make and receive external calls from within the Teams interface they already use. Pricing starts at approximately $8 per user per month as an add-on to existing Microsoft 365 subscriptions, though you’ll also need a Calling Plan or Direct Routing configuration to connect to the public phone network.
Ready to compare specific platforms before committing to a provider? See our VoIP platform roundup for side-by-side pricing, feature, and reliability ratings across the top hosted VoIP services for small and mid-sized businesses.