The CBIC has issued comprehensive guidelines for CGST field formations to ensure uniformity and ease of doing business while undertaking enforcement activities involving regular taxpayers. Here's a summary of the key points:

1. Within the allocated jurisdiction of Commissionerate under notification No. 2/2017-Central Tax dated 19.06.2017, the (Pr.) Commissioner shall be responsible for developing and approving any intelligence, conducting search, and completing investigation in a case and the relevant subsequent action, including in the divisional formations, etc.

2. Investigations must be initiated only with the approval of the Principal Commissioner, except in specific situations requiring approval from the zonal (Pr.) Chief Commissioner as elaborated in the said Instruction. 

3. Prior confirmation of ongoing inquiries by other investigating offices or tax administrations on the same subject matter with respect to the same taxpayer/GSTIN is required before initiating investigations. 

4. When the Commissioner ate discovers that both the DGGI and State GST department are separately investigating the same taxpayer on different matters, the (Pr.) Commissioner must coordinate with both offices to consolidate the investigations under one. If consolidation isn't possible, reasons for maintaining separate investigations must be documented by the (Pr.) Commissioner. 

5. In cases where investigation with respect to a GSTIN in a jurisdiction is initiated but the issue is relevant to some or all of that taxpayers’ GSTINs registered (under the same PAN) in multiple jurisdictions, then the (Pr.) Commissioner shall expeditiously make a self-contained reference to its zonal (Pr.) Chief Commissioner who shall request the Pr. DG, DGGI to take up the matter in accordance with DGGI guidelines. The Instruction also contains the action that shall be taken where the issue is relevant to other taxpayers’ GSTINs registered (under multiple PANs) across various CGST jurisdictions. 

6. In cases where interpretation differences may lead to litigation or practice changes, a reference should be made to the relevant policy wing of the Board i.e. the GST Policy or TRU. This reference should ideally be made before concluding the investigation to promote uniformity and potentially avoid litigation. 

7. Investigations should conclude within one year, and delay in issuing show because notices or closure reports should be avoided. 

8. The Addl./Jt. Commissioner in-charge of investigation is the Grievance Officer whom taxpayers may approach (through letter, email or by appointment) with grievance, if any, related to an ongoing investigation, for appropriate redress. In case the reasonable grievance persists, the (Pr.) Commissioner may consider meeting, by appointment, the taxpayer. 

These guidelines aim to streamline investigation processes, ensure fairness, and prevent undue harassment to taxpayers while maintaining compliance with legal provisions and promoting ease of doing business.