Is there any document to be enclosed along with refund claim? If yes, what are the documents to be submitted

Yes, the following documents are required to be enclosed along with the refund application:
1. Documentary evidence to establish that a refund is due to the applicant
(prescribed under Rule 89(2) of the CGST Rules, 2017, and
2. Documentary evidence to prove that incidence of tax and interest had not been passed on to any other person.

(ICAI FAQ PUBLICATIONS 06-09-2017 REFUNDS: FAQ NO. 13)

Is there any condition to claim refund of unutilised ITC

Yes, and the condition is that supplier of goods or services has not – availed drawback in respect of CGST or claimed refund of IGST paid on such supplies. In other words, no refund of input tax credit shall be allowed if the supplier of goods or services avails drawback in respect of CGST or claims refund of IGST paid on such supplies.

(ICAI FAQ PUBLICATIONS 06-09-2017 REFUNDS : FAQ NO. 12)

Can any person claim refund of any unutilised ITC at the end of the tax period

No, only the following registered persons can claim refund of unutilised ITC:
1. Persons undertaking exports (including other zero-rated supplies). Exception: No refund will be allowed on the goods exported out of India where such goods are subjected to export duty [second proviso to Section 54(3)];
2. Credit has accumulated on account of rate of tax on inputs being higher than the rate of tax on outward supplies (other than cases of nil-rated or fully exempted supplies) except supply of goods or services or both as may be notified by the Government.

(ICAI FAQ PUBLICATIONS 06-09-2017 REFUNDS: FAQ NO. 11)

Can any registered person claim the refund under Section 54

No. Refund can only be claimed under specified circumstances: –
(a) zero rated supplies made without payment of tax
(b) where the credit has accumulated on account of rate of tax on inputs being higher than the rate of tax on output supplies (other than nil rated or fully exempt supplies), except supplies of goods or services or both as may be notified by the Government on the recommendations of the Council           Provided further that no refund of unutilised input tax credit shall be allowed in cases where the goods exported out of India are subjected to export duty:
Provided also that no refund of input tax credit shall be allowed, if the supplier of goods or services or both avails of drawback in respect of central tax or claims refund of the integrated tax paid on such supplies.

(ICAI FAQ PUBLICATIONS 06-09-2017 REFUNDS: FAQ NO. 8)

Can the refund of balance in cash or credit ledger be claimed

Yes, as per provisions of Section 49(6), the balance of cash or credit after payment of tax, interest, penalty, fee or any other amount payment refund can be claimed as per provisions of Section 54.Once the refund is claimed, the amount of credit of CGST/SGST/ IGST (as the case may be) would be reduced to that extent.

(ICAI FAQ PUBLICATIONS 06-09-2017 REFUNDS: FAQ NO. 7)

Are SEZ Units liable to pay taxes on their inward supplies? Who will be eligible for refund of taxes paid on supplies to SEZ

No. SEZ units shall not be charged with taxes for supplies made to them. In respect of supplies to a SEZ unit or a SEZ developer, the application for refund shall be filed by the –
(a) supplier of goods after such goods have been admitted in full in the SEZ for
authorised operations,
(b) supplier of services along with such evidence regarding receipt of services for authorised operations; as endorsed by the specified officer of the Zone.

(ICAI FAQ PUBLICATIONS 06-09-2017 REFUNDS : FAQ NO. 6)