Basic exemption limit determines when individuals and specified entities become liable to income tax under current and new regimes. Basic exemption limits dictate income-tax liability for individuals, HUFs, AOPs and BOIs, with higher exemption thresholds for resident senior and very senior individuals; co-operative societies, firms, companies and local authorities have no basic exemption and are taxable on all chargeable income. A new tax regime option is available to individuals, HUFs, AOPs, BOIs and AJP, carrying a distinct threshold applicable to opt-in assessees and effective from the assessment year specified in the guidance.