"The annualized income for the 2nd annualize period (form 2210 schedule AI line 3b) is over $250,000. The annualized income for the other 3 periods is less than $250,000."
If you are referring to gross income, you are determining the income per period incorrectly. Each of the four periods begins on January 1, so each subsequent period includes the income shown for the previous period. This means the income for each subsequent period has to be at least as much as the previous period. In other words, each period shows gross year-to-date income, where the date is the ending date of the period.
The only way that you could have NIIT apply to period (b) and not to periods (c) and (d) is if you had substantial deductions added in periods (c) and (d) that are less that the income added for those periods.
