My wife only worked for three days and will not owe. Do I have to add her to my returns?

[Carl]

Weather she works or not doesn't matter. If you're married, you're filing Married filing Joint. Any other way is NOT the most tax advantageous to you. Also, regardless of "when" she worked, if she received "any" taxable income in the tax year, it's reportable on your joint tax return.

[xmasbaby0]

If you were married at the end of 2016 your filing choices are married filing jointly or married filing separately.

Married Filing Jointly is usually better, even if one spouse had little or no income. When you file a joint return, you and your spouse will each receive the $4050 personal exemption, plus the married filing jointly standard deduction of $12,600 (add $1250 for each spouse over the age of 65). 

And ALL of your income must be entered on your return, even your spouse's small amount.