Let us look at chapter 14 of CGST rules – Transitional Provisions. This text is taken from http://www.cbec.gov.in/resources//htdocs-cbec/gst/cgst-rules-01july2017%20.pdf
(1) Every registered person entitled to take credit of input tax under section 140 shall, within ninety days of the appointed day, submit a declaration electronically in FORM GST TRAN-1, duly signed, on the common portal specifying therein, separately, the amount of input tax credit of eligible duties and taxes, as defined in Explanation 2 to section 140, to which he is entitled under the provisions of the said section:
Provided that the Commissioner may, on the recommendations of the Council, extend the period of ninety days by a further period not exceeding ninety days.
Provided further that where the inputs have been received from an Export Oriented Unit or a unit located in Electronic Hardware Technology Park, the credit shall be allowed to the extent as provided in sub-rule (7) of rule 3 of the CENVAT Credit Rules, 2004.
(2) Every declaration under sub-rule (1) shall-
(a) in the case of a claim under sub-section (2) of section 140, specify separately the following particulars in respect of every item of capital goods as on the appointed day-
(b) in the case of a claim under sub-section (3) or clause (b) of sub-section (4) or subsection (6) or sub-section (8) of section 140, specify separately the details of stock held on the appointed day;
(c) in the case of a claim under sub-section (5) of section 140, furnish the following details, namely:—
(3) The amount of credit specified in the application in FORM GST TRAN-1 shall be credited to the electronic credit ledger of the applicant maintained in FORM GST PMT-2 on the common portal.
(4) (a) (i) A registered person who was not registered under the existing law shall, in accordance with the proviso to sub-section (3) of section 140, be allowed to avail of input tax credit on goods (on which the duty of central excise or, as the case may be, additional duties of customs under sub-section (1) of section 3 of the Customs Tariff Act, 1975, is leviable) held in stock on the appointed day in respect of which he is not in possession of any document evidencing payment of central excise duty.
(ii) The input tax credit referred to in sub-clause (i) shall be allowed at the rate of sixty per cent. on such goods which attract central tax at the rate of nine per cent. or more and forty per cent for other goods of the central tax applicable on supply of such goods after the appointed date and shall be credited after the central tax payable on such supply has been paid: Provided that where integrated tax is paid on such goods, the amount of credit shall be allowed at the rate of thirty per cent. and twenty per cent. respectively of the said tax;
(iii) The scheme shall be available for six tax periods from the appointed date.
(b) The credit of central tax shall be availed subject to satisfying the following conditions, namely:-
(i) such goods were not unconditionally exempt from the whole of the duty of excise specified in the First Schedule to the Central Excise Tariff Act, 1985 or were not nil rated in the said Schedule;
(ii) the document for procurement of such goods is available with the registered person;
(iii) the registered person availing of this scheme and having furnished the details of stock held by him in accordance with the provisions of clause (b) of sub-rule (2), submits a statement in FORM GST TRAN 2 at the end of each of the six tax periods during which the scheme is in operation indicating therein, the details of supplies of such goods effected during the tax period;
(iv) the amount of credit allowed shall be credited to the electronic credit ledger of the applicant maintained in FORM GST PMT-2 on the common portal; and
(v) the stock of goods on which the credit is availed is so stored that it can be easily identified by the registered person.
Every person to whom the provision of clause (c) of sub-section (11) of section 142 applies, shall within a period of ninety days of the appointed day, submit a declaration electronically in FORM GST TRAN-1 furnishing the proportion of supply on which Value Added Tax or service tax has been paid before the appointed day but the supply is made after the appointed day, and the Input Tax Credit admissible thereon.
Every person to whom the provisions of section 141 apply shall, within ninety days of the appointed day, submit a declaration electronically in FORM GST TRAN-1, specifying therein, the stock of the inputs, semi-finished goods or finished goods, as applicable, held by him on the appointed day.
Every person having sent goods on approval under the existing law and to whom sub-section (12) of section 142 applies shall, within ninety days of the appointed day, submit details of such goods sent on approval in FORM GST TRAN-1.
The amount credited under sub-rule (3) of rule 117 may be verified and proceedings under section 73 or, as the case may be, section 74 shall be initiated in respect of any credit wrongly availed, whether wholly or partly.