It depends on how the phone is going to be used (by whom). Licensing is covered under either CUWL or UCL licensing model, so the easiest way would be to purchase either CUWL Standard or CUWL Pro license which will entitle the owner of the phone to use it along with voicemail account, single number reach, softphone, etc.
If this is standalone phone you can get Public Space UWL license for example.
Whoever you are purchasing this from should know how to quote it.
HTH, please rate all useful posts!
Chirs
