Service tax on customized software..urgent

Hello All,

One of my client develop and customise softwares according to need of clients situated in non taxable territory. Consideration received in foriegn exchange. Firstly software is developed and then it is tested by clients and changes according to their need are done. Will it be a taxable service?? if yes then under which rule of Place of Provision? and if no then reason behind that. Please clarify..