Non-Fixed VoIP Guide: Everything You Need To Know

If your business is considering making the switch to Voice over Internet Protocol (VoIP), it’s important to know that there’s more than one kind of VoIP service.

Traditional VoIP, also known as fixed VoIP, offers digital phone service for a landline phone. Non-fixed VoIP is more flexible, enabling you to assign a phone number that can be used on any device, without a landline.

Many of the best business VoIP providers in the UK offer both fixed and non-fixed VoIP options. In this guide, we’ll explain what non-fixed VoIP is and help you decide if it’s right for your company.

Non-fixed VoIP is a type of VoIP phone service that allows you to make and receive calls from phone numbers that aren’t affiliated with a landline.

Traditional, or fixed, VoIP phone numbers must be associated with a landline at a physical address. This can be limiting since it means you can only get phone numbers for your business premises.

Non-fixed VoIP phone numbers are not associated with a specific landline or address but rather exist entirely on the internet. For this reason, non-fixed VoIP phone numbers are often called virtual phone numbers.

Non-fixed VoIP phone numbers can be created for any business, person, or device. There’s no limit to how many non-fixed VoIP phone numbers a single entity or device can have. In addition, non-fixed VoIP numbers aren’t limited by geography. For example, you can get a US phone number even if you’re located in the UK.

Why Use Non-Fixed VoIP?

There are several reasons why businesses might prefer non-fixed VoIP over a traditional fixed VoIP system. Let’s look at a few potential use cases.

Supporting Remote and Hybrid Work Arrangements

Employees typically use their smartphone or computer to make and receive calls over a non-fixed VoIP phone system. So, instead of assigning a phone number to each desk phone in your office, you can assign a phone number to each individual employee.

This supports businesses that offer remote or hybrid work options or whose staff travel frequently for work. Employees can make and receive calls from the same number no matter whether they’re in the office, at home, or travelling on business. You no longer have to worry about setting up call forwarding from one desk phone to another when an employee is out of the workplace.

Officeless Businesses

You can also use non-fixed VoIP to establish a phone service for a fully remote business—that is, a business without a centralised office. This isn’t possible with traditional VoIP phone systems, which require your business to have a physical address for your primary phone number.

With a non-fixed VoIP system, you can set up a virtual number for your business that answers with an auto-attendant when customers call. They’re then forwarded to the right employee based on which menu option they select.

Giving Your Business a Global Presence

The geographic flexibility of a non-fixed VoIP service can also make a huge difference for businesses with international customers. You don’t need an office in a specific country to get a local number.

As an example, your business can get a virtual phone number with a US area code, even if you don’t have an office there. You can use this number to call US customers or give out that number to customers who need support, making your company appear more professional and customer-oriented to international clients.

Non-Fixed VoIP vs Fixed VoIP: What’s the Difference?

Both fixed and non-fixed VoIP systems route calls over the internet, meaning you get many of the key benefits of VoIP with a non-fixed system. However, there are some important differences in how fixed and non-fixed VoIP phone systems work in practice.

Physical Address

With a fixed VoIP service, you must have a physical address. Your phone number is tied to this address and must match the number conventions for that address. For example, you can’t have a US number assigned to an office in the UK.

With a non-fixed VoIP service, you can get a number for anywhere in the world without an address. You don’t need to have an office in, say, Germany to get a German phone number.

Landline Phones

Every fixed VoIP phone number is assigned to a specific landline phone, which means you can only have as many phone numbers as you have landlines.

Non-fixed VoIP phone numbers don’t require landline phones, and most businesses use smartphones or computers to make calls with a non-fixed VoIP phone service. You can assign unlimited phone numbers to an account and toggle between them when making calls.

International Calling

When you make a call to another country using a fixed VoIP service, you’ll often pay hefty international calling fees. There’s no way to avoid these fees short of opening an office in another country and setting up a phone line there.

With a non-fixed VoIP service, on the other hand, you can simply get a phone number for the country you want to call. If you call Italy from an Italian phone number, it’s billed as a local call even if you’re located in the UK when you make the call. This can dramatically reduce international calling costs.

999 Emergencies

When you dial 999 with a fixed VoIP phone number, call handlers immediately receive your address and can send help. However, when you dial 999 from a non-fixed VoIP number, emergency medical dispatchers won’t automatically know where you’re located.


Non-fixed VoIP has been negatively associated with spammers who use the service to hide their location from authorities. It also increases the effectiveness of some scams since those targeted may incorrectly believe the caller is located in a particular area based on the phone number.

It’s much more difficult to use fixed VoIP phone numbers for spam calling as authorities can quickly track down where the calls are coming from.


One of the biggest advantages of choosing a non-fixed VoIP service for your business is that it’s often cheaper than its fixed alternative. Not only can you reduce or eliminate international calling fees, but many VoIP providers also charge less for non-fixed VoIP plans.

You also don’t have to pay for VoIP-enabled desktop phones or worry about wiring additional landlines into your business premises as your workforce grows.

Non-Fixed VoIP Pros and Cons


  • Doesn’t require your business to have landlines or a physical office
  • Doesn’t require desktop phones—employees can use their computer or smartphone to make and receive calls
  • Enable employees to take their phone number with them no matter where they’re working
  • Get numbers for multiple countries around the world to give your business a local presence for international customers
  • Reduce international calling fees
  • Often less expensive than fixed VoIP phone service


  • Emergency services won’t automatically receive your location when you dial 999
  • Your business’ name won’t appear on a recipient’s caller ID when making calls

Tips for Using Non-Fixed VoIP

Here are a few tips to help your business get the most out of a non-fixed VoIP system.

Start Calls by Giving Your Company Name

When you make a call to a customer from a non-fixed VoIP number, their caller ID will likely display the city or country associated with your phone number, but not your business’ name. So, customers may sound wary or confused when they first answer.

To get the conversation on the right track, it’s a good idea to start every call by giving your name and your company’s name.

Record a Professional Voicemail Greeting

Recording a professional-sounding voicemail greeting for your non-fixed VoIP phone number is another way to give your business more legitimacy in customers’ eyes. Your greeting should include your name and your business’ name, plus details like your support hours or how long it typically takes to respond to enquiries.

Post Your Phone Numbers Online

In some cases, customers won’t answer the phone if it’s an unfamiliar number. Instead, they’ll search the number online to see who it belongs to, then call back once they discover it’s not spam. To ensure that customers can associate your phone numbers with your business, it’s a good idea to post your numbers on your website and online business directories.

A great approach is to list phone numbers by country on your support page. That way, customers will call your local phone number and they won’t pay international calling fees.

Next Steps

Non-fixed VoIP enables you to get a virtual phone number that isn’t associated with a specific address or landline phone. You can use non-fixed VoIP to assign dedicated phone numbers to individual employees and let them use their numbers on any device. It’s a great way to reduce international calling fees, establish your business’ global presence, and improve customer service.

There are relatively few drawbacks to non-fixed VoIP phone systems, so it’s worth considering if you’re transitioning your workforce to a VoIP phone system.

Frequently Asked Questions

Can you text a non-fixed VoIP phone number?
Non-fixed VoIP phone numbers support both SMS and MMS text messages. They work just like fixed VoIP phone numbers for text messaging. Depending on your phone plan, you may have to pay extra for text messaging.
Can you track a non-fixed VoIP phone number?
There’s no way to track a non-fixed VoIP phone number to a specific location or address. That’s because these phone numbers can be used from anywhere in the world. The best way to find out who’s behind a non-fixed VoIP phone number is to contact the phone company that assigned the number.
Can I use a non-fixed VoIP number with a landline phone?
Landline phones typically use fixed VoIP phone numbers, but you can also use them with non-fixed phone numbers. Landline phones must be VoIP-enabled and work with your provider’s software. You’ll need to use the software to assign a virtual phone number to the landline phone.
Written by:
Michael is a prolific business and B2B tech writer whose articles have been published on many well-known sites, including TechRadar Pro, Business Insider and Tom's Guide. Over the past six years, he has kept readers up-to-date with the latest business technology, corporate finance matters and emerging business trends. A successful small business owner and entrepreneur, Michael has his finger firmly on the pulse of B2B tech, finance and business.
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James thinks all businesses can improve if they use the right technology. At Expert Market, he utilises his 4+ years experience as a researcher to offer specialised advice on a wide range of categories from CRM to Fleet Management.