Can the person chargeable with tax pay the amount of demand along with interest before the service of show cause notice under sub-section 73(1) or statement under section 73(3)

Yes. The person chargeable with tax can pay the amount of tax along with interest under section 50 based on his own ascertainment of such tax or the tax as ascertained by the proper officer and inform the proper officer in writing of such payment in Form GST DRC-03. On receipt of such information, the proper officer shall issue an acknowledgement for accepting the payment made by the said person in Form GST DRC-04 and shall not serve any notice or statement with respect to the tax so paid.

(ICAI FAQ PUBLICATIONS 06-09-2017 Determination of tax not paid or short paid or erroneously refunded or input tax credit wrongly availed or utilized for any reason other than fraud or any willful misstatement or suppression of facts: FAQ NO. 4)

Whether proper officer can issue similar show cause notice for any periods other than those covered under section 73(1)

Yes. The proper officer may serve a statement under section 73(3) along with a summary electronically in Form GST DRC-02 containing details of tax not paid or short paid or erroneously refunded or input tax credit wrongly availed or utilized where the grounds relied upon by the proper officer for such periods are the same as are mentioned in the earlier notice issued under section 73(1). The service of such statement shall be deemed to be service of show cause notice on the person chargeable with tax.

(ICAI FAQ PUBLICATIONS 06-09-2017 Determination of tax not paid or short paid or erroneously refunded or input tax credit wrongly availed or utilized for any reason other than fraud or any willful misstatement or suppression of facts : FAQ NO. 3)

What is the time limit for issue of show cause notice by the proper officer under section 73(2)

The proper officer shall issue show cause notice at least 3 months prior to the time limit of 3 years for issuance of order i.e.
 Before completion of 3 years from the due date for furnishing of annual return for the financial year to which the tax not paid or short paid or input tax credit wrongly availed or utilized relates to, or
 within 3 years from the date of erroneous refund, as the case may be.

9ICAI FAQ PUBLICATIONS 06-09-2017 Determination of tax not paid or short paid or erroneously refunded or input tax credit wrongly availed or utilized for any reason other than fraud or any willful misstatement or suppression of facts : FAQ NO. 2)

Under what circumstances, the proper officer shall invoke provisions of section 73(1) to serve show cause notice on the person chargeable with tax

The proper officer shall serve notice under the provisions of Section 73(1) along with a summary, electronically in Form GST DRC-01 (as per Chapter XVIII-Demands and Recovery of the CGST Rules) on the person chargeable with tax for any reason other than:
 fraud
 willful misstatement
 suppression of facts,
when he has reasons to believe that tax has not been paid or short paid or erroneously refunded or input tax credit has been wrongly availed or utilized.

(ICAI FAQ PUBLICATIONS 06-09-2017 Determination of tax not paid or short paid or erroneously refunded or input tax credit wrongly availed or utilized for any reason other than fraud or any willful misstatement or suppression of facts: FAQ NO. 1)

Are there any other class of officers who are required to assist proper officers in implementation of the CGST Act,2017

Under Section 72 of the CGST Act,2017, the following officers are required to assist proper officers in the implementation this Act. The categories specified in Act are as follows:
(a) Police
(b) Railways
(c) Customs
(d) Officers of State/Union Territory engaged in collection of GST
(e) Officers of State/Central Government engaged in collection of land revenue
(f) All village officers
(g) Any other class of officers as may be notified by the Government.

(ICAI FAQ PUBLICATIONS 06-09-2017 Officers required to assist proper officers: FAQ NO. 23)

Can the proper officer access business premises of a registered taxable person

Yes. An audit party of CGST or a cost accountant or chartered accountant nominated under section 66 have access to any business premises without issuance of a search warrant for the purposes of carrying out any audit, scrutiny, verification and checks as may be necessary to safeguard the interest of revenue. Further, in terms of section 70(1), an officer authorised by a proper officer not below the rank of Joint Commissioner can also have access business premises of a registered person.

(ICAI FAQ PUBLICATIONS 06-09-2017 Access to business premises : FAQ NO. 22)

What can be the consequences of non-appearance to summons

The proceeding before the proper officer who has issued summons is deemed to be judicial proceedings. If a person does not appear on the date when summoned without any reasonable justification, he can be prosecuted under section 174 of the Indian Penal Code (IPC). If he absconds to avoid service of summons, he can be prosecuted under section 172 of the IPC and in case he does not produce the documents or electronic records required to be produced, he can be prosecuted under section 175 of the IPC. In case he gives false evidence, he can be prosecuted under section 193 of the IPC.

(ICAI FAQ PUBLICATIONS 06-09-2017 Power to summon persons to give evidence and produce documents : FAQ NO. 21)

What are the responsibilities of the person so summoned

A person who is issued summon is legally bound to attend either in person or by an authorized representative and he is bound to state the truth before the officer who has issued the summon upon any subject, which is the subject matter of examination and to produce such documents and other things as may be required.

(ICAI FAQ PUBLICATIONS 06-09-2017 Power to summon persons to give evidence and produce documents : FAQ NO. 20)

When can the proper officer issue summons

Section 70(1) gives powers to the proper officer to call upon any person by issuing a summon to be physically present before him to either give evidence or produce a document or any other thing in any inquiry in the same manner, as provided in the case of a civil court under the provisions of the Code of Civil Procedure, 1908.

(ICAI FAQ PUBLICATIONS 06-09-2017 Power to summon persons to give evidence and produce documents  : FAQ NO. 19)

What are the safeguards provided for a person who is placed under arrest

The following are the safeguards provided for a person who is placed under arrest:
(a) If a person is arrested for a cognizable offence, he must be informed in writing of the grounds of arrest and he must be produced before a magistrate within 24 hours of his arrest;
(b) If a person is arrested for a non-cognizable and bailable offence, the Deputy/ Assistant Commissioner shall, for the purpose of releasing an arrested person on bail or otherwise, have the same powers and be subject to the same provisions as an officer-in-charge of a police station.                              All arrest must be in accordance with the provisions of the Code of Criminal Procedure, 1973 relating to arrest.

(ICAI FAQ PUBLICATIONS 06-09-2017 POWER TO ARREST: FAQ NO. 18)