If my flatmates are not using Landlords PAN, can I inflate my rent to get more tax rebate?
Yes. You 'can'. It would however be illegal. You pay tax on your personal income, and you're given rebate for certain personal expenditures. The rent your flatmates pay for is not your personal expenditure. Even if you had their consent to do so, your effective income would go up proportional to your rent payments (they pay you rent, you pay rent to landlord), nullifying the rebate. In the real world, there is a very tiny chance that you'll get caught doing this akin to being charged for littering. But, it is not legal, and personally I would prefer my peace of mind over the saved taxes.