I thought I heard there was one court case of a sovereign citizen who asked the question of the prosecution where in the tax code it says that paying federal taxes is the law. When the prosecution was unable to prove or show that the tax code does say it is a law the defendant won the case. Plus knowing that the writers of the constitution did not want a federal tax imposed why is it now mandatory.
The US has changed since the eighteenth century, and so the framers wisely made provision for the Constitution to be changed in ways that they themselves might not have envisaged or wanted. The 16th Amendment in 1909 specifically authorised a federal income tax.