Yes, if you are filing a joint return you have to enter all of your income for each of you. You cannot wait and enter a 2015 W-2 on next year's 2016 tax return.
Every W-2 that you and your spouse received must be reported on your tax return, even if they are for small amounts. Remember that each one of those W-2’s has your Social Security number on it, and that income was reported to the IRS by the employer. You do not want to get in trouble with the IRS for under-reporting your income.
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