India could look at a calibrated increase in the goods and services tax-rates to shield consumers from sudden price-shocks, apart from minimising exemptions, as it seeks to lift tax-revenue-collections. A panel of officials on revenue-augmentation, comprising officials from states and Centre, is reviewing the current rate-structure. States such as Punjab suggested slabs of 10% and 20%, with a-third-rate of 25% for sin and luxury-goods.