CBIC has issued Circular No. 41/2018 - GST dated 13/04/2018 laying down the procedure for interception of conveyances for inspection of goods in movement, and detention, release and confiscation of such goods and conveyances.
The gist of the circular is as under:

•  Interception of conveyances for verification of documents and/or Inspection of goods can be carried out by officers of the Inspector level or above designated as proper officer for the purpose by the commissioner.
•  Person in charge of the conveyance in case of transportation by road should carry Invoice/Bill of Supply/Delivery Challan and copy of E-Way Bill in physical form or E-Way Bill number in electronic form.
•  If prima facie no discrepancy is found in documents the conveyance shall be allowed to move further.
•  If the documents are not produced or the officer intends to carry out inspection he will record a statement of the person in charge of conveyance in FORM GST MOV-01.
•  The officer shall also issue an order for inspection in FORM GST MOV-02.
•  The officer shall upload his first report in Part A in FORM GST EWB-03 on the common portal within 24 hours of the issuance of FORM GST MOV-02.
•  The officer shall conclude inspection within 3 working days of the issuance of FORM GST MOV-02 and prepare a final report in Form GST MOV-04 and upload the same in Part B of FORM GST EWB-03 on the common portal.
•  Extension of this period of 3 working days is possible by the commissioner. Written permission to be given in FORM GST MOV-03.
•  If no discrepancy found in inspection, officer to issue release order in FORM GST MOV-05 and allow the conveyance to move further.
•  If the officer decides to detain the conveyance and goods he shall issue detention order in FORM GST MOV-06.
•  He shall also issue a notice specifying the tax and penalty payable on the person in charge of the conveyance in FORM GST MOV-07.
•  Where the tax and penalty is paid the officer shall release the conveyance and the goods and upload an order in FORM GST MOV-09 on the common portal.
•  The demand of the duty and the payment thereof shall be reflected in the relevant electronic ledgers of the concerned person.
•  The conveyance and the goods can also be released on a bond in FORM GST MOV-08 along with a bank guarantee equal to the amount payable.
•  Where any objections are filed the proper officer shall pass a speaking order quantifying the tax and penalty.
•   If the proposed tax and penalty are not paid within 7 days of date of detention a notice for confiscation of goods and conveyance and imposition of penalty shall be issued in FORM GST MOV-10.
•  In case of conveyance used on hire basis the owner can be issued a notice for imposition of fine equal to tax payable on goods in lieu of confiscation of conveyance.
•  An order of confiscation of goods and conveyance and imposition of fine in lieu of confiscation can be issued in FORM GST MOV-11 only after considering the objections filed and giving an opportunity of personal hearing.
•  The order shall be served upon the person concerned.
•  Maximum time available for making payment of tax, penalty and fine is three months.
•  If the dues are not paid within 3 months, the proper officer shall auction the goods and/or conveyance by public auction.
•  Corresponding order shall be passed by the officer under respective SGST Act or UTGST Act.
•  The procedure narrated above applies mutatis mutandis under IGST Act.