When do amt taxes kick in?

There is no easy answer. Without getting into all the gory details, AMT kicks in if your AMT income amount (which is equal to your adjusted Gross Income less charity and mortgage interest deductions) minus the AMT exemption, when taxed at 26% for ordinary income and 15% for capital gains and dividends, exceeds the amount that taxes figured the "normal way" would be. The AMT exemption amount varies from $82,000 if income < $156,500 down to $0 for income > $484,900. In general AMT ensnares those with pretty high non-AMT deductions, such as state and local taxes or investment expenses.

AMT follows individual cases. There is no particular when. Once you calculate your adjusted minimum taxable income, Form 6251 allows you to claim an AMT exemption that is based on your filing status. The simplest way is to look at your Form 6251 from last year.

Compare the Tentative Minimum Tax to your regular tax (Tentative Minimum Tax should be the line above your regular tax) to see how close you were to paying the AMT.
Look for entries on lines 1-27, which adjust your taxable income for AMT purposes. For instance, you have to put various items back into your income, adding such items as your standard deduction, personal exemptions, home equity mortgage interest, miscellaneous deductions such as employee business expenses, and the bargain element of any incentive stock options you exercised.

If you Google Alternative Minimum Tax, you will find lots of information, far more than we could put in "layman's terms"

In short, there is NO set answer about when AMT kicks in. It depends on the individual circumstances of each taxpayer.