What is Alternative Minimum Tax (AMT)?
The AMT is a parallel tax system that ensures higher-income taxpayers pay a minimum amount, by disallowing certain deductions.
How it works
You calculate your tax the normal way and again under AMT rules — which add back items like large state-tax deductions and certain stock-option gains — then pay whichever is higher. An AMT exemption shields most middle-income filers from it entirely.
A quick example
What people get wrong
The classic AMT trap is exercising ISOs and holding the shares. If you're doing that, model the AMT hit before year-end — the tax can come due on gains you haven't actually pocketed.