Please see this answer from MaryK. It may address your issue.
You do not have to, but it may help you for the Earned Income Tax Credit.
You can elect to include your nontaxable combat pay in earned income for the earned income credit. If you make the election, you must include in earned income all nontaxable combat pay you received. The amount of your nontaxable combat pay should be shown on your Form W-2 in box 12 with code Q.
Electing to include nontaxable combat pay in earned income may increase or decrease your EIC. Figure the credit with and without your nontaxable combat pay before making the election. Whether the election increases or decreases your EIC depends on your total earned income, filing status, and number of qualifying children. If your earned income without your combat pay is less than the amount shown below for your number of children, you may benefit from electing to include your nontaxable combat pay in earned income and you should figure the credit both ways. If your earned income without your combat pay is equal to or more than these amounts, you will not benefit from including your combat pay in your earned income.
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