There are two issues.
Your expenses are "qualified expenses" for any month where you and your spouse both worked or looked for work. The allowable credit is $500 per month for each month she worked or looked for work.
However, the maximum expense allowed is the amount of money she actually reports as taxable income for the year.
This creates some interesting situations because the tax form does not break things down month by month, you are on the honor system to do that. Suppose she is paid $6000 in December, but was only "looking for work" for 4 months. That means that only $2000 of your expenses are qualified. But the form only asks for the amount of qualified expenses and her income, it doesn't break it down by month. So you could enter $6000 of qualified expenses and get the full credit, and the IRS wouldn't know it was wrong unless they audited you. On the other hand, if she was looking for work for all 12 months, but is only paid $2000 in 2017, then all your expenses are "qualified" but your maximum credit is still only $2000.
