provision on sale of goods approval basis to another state

U will have to register as casual taxable person making taxable supply.

goods return on unsold treatment ????

A casual taxable person or a non-resident taxable person shall, at the time of submission of application for registration under sub-section [1] of Section 25, make an advance deposit of tax in an amount equivalent to the estimated tax liability of such person for the period for which the registration is sought:

Provided that where any extension of time is sought under sub-section [1], such taxable person shall deposit an additional amount of tax equivalent to the estimated tax liability of such person for the period for which the extension is sought.

[3] The amount deposited under sub-section [2] shall be credited to the electronic cash ledger of such person and shall be utilised in the manner provided under Section 49.

Provided that a casual taxable person or a non-resident taxable person shall apply for registration at least five days prior to the commencement of business.