Rule 10A In GST.......

Furnishing of Bank Account Details.-After a certificate of registration in FORM GST REG-06 has been made available on the common portal and a Goods and Services Tax Identification Number has been assigned, the registered person, except those who have been granted registration under rule 12 or, as the case may be rule 16, shall as soon as may be, but not later than forty five days from the date of grant of registration or the date on which the return required under section 39 is due to be furnished, whichever is earlier, furnish information with respect to details of bank account, or any other information, as may be required on the common portal in order to comply with any other provision.”.
Query 1:- in this rule term "date on which return required under the section 39 is due to be furnished" means which return GSTR 1 or GSTR 3B and which month month return?