Can a CGST/SGST officer access business premises under any other circumstances?

Yes. Access can also be obtained in terms of Section
64 of MGL. This provision of law is meant to allow an
audit party of CGST/SGST or C&AG or a cost accountant
or chartered accountant nominated under section 50 of
CGST/SGST Act, 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. However,
a written authorization is to be issued by an officer of the
rank of Additional/Joint Commissioner of CGST or SGST.
This provision facilitates access to a business premise
which is not registered by a taxable person as a principal
or additional place of business but has books of accounts,
documents, computers etc. which are required for audit or
verification of accounts of a taxable person.