I'm not sure the OECD is the right comparison point because many OECD members (the Latin American and Eastern European countries, mostly) collect far less in tax revenue than the "more developed" OECD nations like the United States, France, Germany, Sweden or Japan. To use your example of India (I know India isn't in the OECD but it has good tax data, has been studied extensively, and its tax regime isn't miles away from the "less developed" OECD nations) - India collects somewhere on the order of 10% of its national income every year in taxes; the other countries mentioned are in the 40-70% range. For a country that only wants to collect 10% of its national income in taxes it's easy to get away with the (relatively simple) mechanism of consumption taxes; to collect more revenues increasingly progressive forms of taxation, such as income taxes, are required.

Well the UK is at 40% too if you also include national insurance contributions, but both income tax and national insurance are calculated by employers and paid automatically out of your payslip (PAYE). This means most people never have to think about doing a tax return, and also means it’s harder to hide earnings for most people.

There is then a process where people with more complex tax affairs then fill in a government questionnaire on a website which instantly calculates the tax rebate/payment required and adjusts your tax balance.