Your company has two or more offices, study the itemised phone bills over say the last three months.
How much was spent on inter-office phone calls?

Does each office have, or could have, a broadband (cable or ADSL) Internet connection?

Using the VoIP capability of the TaPBX would cut out the cost of those calls, with the added bonus that the existing traditional phone lines would become available for incoming calls.

By linking the offices in this way incoming calls can be transferred within the group of offices transparently.  Personnel who move from one office to another become available, the frustration of a client trying to find the person to talk to them disappears immediately.

In the case of short term absence from an office, calls can be redirected to another office without incurring extra charges from the phone company.

Further savings can be made by using the VoIP link to take advantage of lower call charges if  the offices are within different charging zones.

For example, a company with offices in Paris and Marseille could use the VoIP link to "trunk" calls, so that the Marseille office could use an outgoing phone line from the Paris office to call clients and suppliers in and around Paris and vice versa.  The dial plan incorporated in the TaPBX would be constructed to enable this automatically.