You might be inadvertently "deducting" it twice. In most cases, your HSA contribution has already been reported in Box 12 of your W-2 with code W: Employer Contributions to Health Savings Account and already excluded this amount from your income reported in box 1.
Despite the misleading name, code W reports both your and your
employer's contribution. (A better name would be "Contributions to
Health Savings Account" but we have no say in the matter.) So if you put $1,500 in your HSA during 2015, and your employer
matched your contribution, your W-2's Box 12 should have the amount of
$3,000 with a code W.
Now, if you made HSA contributions not reported on your W-2 (this is uncommon), we'll ask about that when you step through the Medical section. Look for the questions Were HSA contributions made in 2015? or Do you need to make any adjustments to your HSA contribution amount? Answer Yes and we'll open a screen where you can enter that information.
