Can I write off day care even if my child lives with her mom and I pay for half the cost?

The Child Care Credit can only be claimed by the custodial parent.

Who can claim the exemption and credits for a dependent child depends on who is the custodial parent per IRS definition (not court definition).

The test that the IRS uses to determine the custodial parent is where the child lived for more than 1/2 (or greater part) of the year.  For parents who share time equally, such as the mother having 183 days and the father 182 days, the custodial parent is the one with the higher adjusted gross income.

Only the Custodial parent can claim:

• Head of Household
• Earned Income Credit
• Child Care Credit

The non custodial parent can only claim:

• The Exemption
• The Child Tax Credit

The IRS has special rules for divorced or separated parents (or parents who live apart.)

http://www.irs.gov/publications/p17/ch03.html#en_US_2014_publink1000204295