Marginal relief limits surcharge impact where income marginally exceeds threshold, capping combined tax so excess income isn't overtaxed. Marginal relief prevents an excessive increase in combined income-tax and surcharge when total income marginally exceeds a prescribed threshold by ensuring the net increase in tax does not exceed the excess income. Compute tax on the threshold amount, add surcharge applicable to that threshold-tax, add tax on the excess income, and compare with the normal surcharge-inclusive liability; the difference determines the surcharge payable under marginal relief, after which statutory cess is added.