Why exempt supply includes non taxable supply

The inclusion of non-taxable supply inside the definition of exempt supply highlighted is a deliberate legal fiction created by lawmakers. While non-taxable supplies sit outside the levy of GST, bundling them under the "exempt supply" definition ensures that businesses must count their non-GST revenue when calculating threshold limits for Aggregate Turnover (Section 2(6)) and must proportionally reverse input tax tax-credits on common business expenses under ITC Reversal rules (Section 17(2) & (3)).