Long Distance Calling

• Almost all VoIP providers offer domestic long distance calling as part of the monthly fee; you might have to pay an extra charge for international calls. Residential plans sometimes limit the number of long distance calls or include only calls to people using the same VoIP service. Business VoIP plans are more likely to include unlimited calls to and from any number in the same country but might charge an extra fee, known as bursting, if you exceed a certain number of calls at one time.
  
  

Inbound Call Features

• VoIP providers offer caller ID that displays the caller's phone number on your phone or computer screen. If you are using the phone and another call comes in, a call stacking, or call waiting, feature lets you see the number. Unanswered calls go to voice mail, which you can route to email. Call blocking lets your system refuse calls from one number or a group of numbers.
  
  

Outbound Call Features

• Depending on the provider and equipment you select, you can place calls from your computer or phone keypad. A phone book feature, similar to speed dial, lets you select a name to call without dialing a phone number. Conference calling lets three or more parties talk on the same call.
  
  

Number Assignment and Portability

• VoIP plans let you keep the phone number you already use, or you may opt for a new one. You can select a specific area code even if your phone system is not based in that area code's service area. Because VoIP assigns Internet bandwidth, not dedicated phone lines, to your account you can make and receive calls using just one number.
  
  

Equipment, Security and Redundancy

• Security and redundancy are important features to consider when selecting a VoIP provider.Chad Baker/Photodisc/Getty Images
  
  VoIP equipment varies with the plan and provider. Some VoIP plans offer equipment that looks like a regular phone but plugs into a high-speed Internet connection instead of a phone jack. Other plans include an adapter, a device that connects your existing telephone to the Internet. Still others allow you to use your computer as a telephone. Look for anti-spitting or anti-spamming protection and, if you plan to use your computer, install antivirus protection.
  
  VoIP service functions as long as your Internet connection is working. If you cannot tolerate a service outage, look for a provider with redundancy -- typically backup servers in multiple locations -- and an administrative service that can reroute calls to another phone number. Redundancy services are more common with business plans.