QUESTION: Will violation of any principle of sound tax system invalidate a tax law?

QUESTION: Will violation of any principle of sound tax system invalidate a tax law?

As a rule, no. Principles of sound tax system are mere guidelines. However, a violation of the principle of theoretical justice may result in the invalidity of a tax law not because of a violation of the canon of taxation but because of a violation of a constitutional mandate requiring that taxation be uniform and equitable and based on a progressive system.