There is no legal/illegal legislation in India so you do not have to pay a tax on bitcoin as long as you store that amount in the form of Bitcoins and do not transfer it to Indian Rupee.
Whenever you convert your crypto to Indian Rupee and make some profit/income, you must pay taxes (According to Income tax.)
Since you are an investor and you process the transfer or withdrawal to your account once or several times during the financial year, you will benefit from Section 44ADA of Income Tax, So you don't have to keep any record. Just think about the total receipts and pay the tax at least 50% of the receipts.
you can read this example for more:
Example: I withdrew Rs. 10,00,000 during the financial year in my bank. Then I will show Rs. 10,00,000 as receipts from my consultancy business. As per Section 44ADA, I have to show my profits to be Rs. 5,00,000 or more (52-55% recommended), let say I show profit to be Rs. 5,20,000. Then I have to pay tax on Rs. 5,20,000 which will be around Rs. 14,000 or zero if I claim deductions of Rs. 20,000 or more (such as LIC premium paid, etc.).
Source and more info ---->
https://bitcointalk.org/index.php?topic=5206607.0