Self-assessed tax inclusion clarified: tax on outward supplies furnished under section 37 but omitted from return now included. Insertion into sub-section (12) of section 75 specifies that self-assessed tax includes the tax payable in respect of details of outward supplies furnished under section 37 but not included in the return furnished under section 39, thereby treating such omitted outward-supply entries declared under section 37 as part of the taxpayer's self-assessed tax liability for the purposes of that sub-section.