If a S Corporation has a taxable income of $100,000, what would be the income tax liability be?

Answer 1

An S-Corp is a pass-though entity so the income passes directly to the shareholder(s)' tax returns. Without knowing how many shareholders and each of their individual financial and tax situations there's no possible way to estimate what the ultimate tax liability would be. It could be as little as $0 or as much as around $20k or so.

Answer 2

S corp income passes through to the owner, combines with whatever other income he or she might have, and tax is then calculated. Not enough info in your question to tell how much that would be.