GST field officers will now have to seek the approval of their zonal principal chief commissioners to initiate an investigation against any big industrial houses or major MNCs and levy duty on goods/services for the first time. The Central Board of Indirect Taxes and Customs (CBIC) has issued guidelines for Central GST (CGST) officers. According to the guidelines, when a taxpayer is simultaneously being investigated by the state GST and DGGI officers on different subject matters, the principal commissioner will "consider the feasibility" of only one of the offices pursuing all the cases with respect to the taxpayer. The guidelines have also set a deadline for tax officers to conclude an investigation within one year of their initiation. CBIC further said that in initiating an investigation with respect to a listed company or PSU or seeking details from them, the CGST officers should issue "official letters instead of summons" to the designated officer of the entity, detailing the .