Service tax-reverse charge method applicability?

Is the reverse charge applicable on services provided and complete before 1.7.2012 though payments or invoice were made after 1.7.2012? sir if service was provided in 12 June 2012 but invoice is raised on 8 Aug-2012 then whether service receiver is liable to pay service tax under reverse charge as POT is 12 June-2012

Thanks in advance for all.