In 1895, the United States Supreme Court ruled a direct income tax to be unconstitutional in the case of Pollack v. Farmers Loan and Trust. In 1913 the 16th Amendment, the income tax amendment, was added to the Constitution. 

So if a direct tax is unconstitutional, Why Pay Taxes?

An official IRS publication says the 16th Amendment to the Constitution requires citizens to pay tax on their income. In ruling on that amendment shortly after it was passed, the US Supreme Court said it; “conferred no new power of taxation”…” it does not extend the taxing power to new or excepted subjects”…” did not authorize any new type of tax”… “

Interesting! So, again, Why Pay Taxes?