Under rule 31 of the CGST Rules, 2017, how is the value of a supply determined when it cannot be determined under rules 27 to 30?

Rule 31 of the CGST Rules is the residual method: where value cannot be determined under rules 27 to 30, it is determined using reasonable means consistent with the principles and general provisions of section 15 and the valuation chapter. Like kind and quality is a test within rule 27 or 28, and 110% of cost is rule 30; best judgment under section 62 is an assessment of non-filers, not a valuation method.