Even a democratic system needs rules and regulations to function harmoniously. However, not having a choice whether to pay or not to pay Income tax is undemocratic.
While most of us pay for:
On top of that we pay huge amount of taxes on petrol/diesel and also sales/service tax.
Putting sales/service tax still be considered voluntarily as we pay it only when we buy stuff or consume any service, however income tax has no bit of democratic choice.