There are a couple of things at play.
There is a childcare tax credit, based on the amount you spend on daycare; it’s a percentage of what you spend that varies inversely per your income. For example, we can take a credit of 20% of what we spend in childcare, up to a cap of 3,000 per kid or 6,000 total for the family (and it is 6,000, or at least was last year per the tax return copy I happened to have near to hand). If our income were lower, we’d take a higher percentage of that 6,000. That also goes away when the child turns 13. http://www.irs.gov/newsroom/article/0,,id=106189,00.html (I think you can claim it for an older child or other family member if the family member is disabled).
Then there’s the separate child tax credit, which you get even if you don’t have daycare expenses. That also phases out as income increases; I don’t know at what level it goes away completely but some years we haven’t gotten anything, last year we got 750.00. Info here.
Your job may also offer a pre-tax account where you can set aside up to 5,000 dollars for dependent care expenses, pre-tax. Generally you’re better off using the pre-tax account rather than using the 6,000 for calculating the tax credit. For example if your tax bracket is 25% and you pay 5% in state taxes, you’d save 30% of the 5,000 dollars (or 1500 dollars), plus I believe there is no social security taken out so there’s another 6.85% savings. Whereas that same 5,000, if you got the 20% credit, would save you 1,000 on your taxes. You should look at the numbers using your own income and see which benefits you more (if you’re lower income, you might get a better deal avoiding the pre-tax account and just taking the federal tax credit).
The childcare tax credit used to have a ceiling of 2500 per kid, so for my 2 kids, it matched the flex spending figure. Now that they’ve raised that to 3,000 per kid, the total is 6,000 - so I get to calculate the childcare tax credit on the difference between the flex spending ceiling of 5000 and the limit of 6,000. That saved me 200 dollars a year (20% of 1,000) the last couple of years. Dweezil however is now over age 13, so we won’t get to do that any more.