Tank full of issues in bringing petrol and diesel under GST state governments derive a lion’s share of revenues from sale of these fuels and bringing them under the GST ambit would mean a sharp decline in revenue, which then will have to be compensated. Union petroleum minister Dharmendra Pradhan said last week that petroleum products should be included under the goods and services tax (GST). That should help consumers pay a rational price at a time w hen diesel and petrol prices are touching multi-year highs.This makes sense. Even if petrol and diesel are taxed at the highest GST slab of 28%, it would be lower than taxes already being paid and result in lower retail prices, helping consumers. Also, those industries which might be using them as inputs could claim input tax credit if these are bought under GST.Cast your eyes on Chart 1 below. CARE Ratings assumes that instead of an effective tax rate of 100% on petrol and 66% on diesel, GST of 90% and 80% are applied on pet...