Click "edit" next to the child's name in the list of dependents and follow the interview questions. If the child did not live with you more than half the year, then say so (choose 5 months or less, an approximate guess is fine). You will then be asked if the other parent will be signing a release form, answer No. The program should determine that the child is not a dependent this year. Or, simply delete them from the list of dependents completely.
If the child does live with you more than half the year, there are certain benefits you may be entitled to even if you sign the release for the non-custodial parent. Answer that the child lived with you more than half the year, (7 months or longer), and that you will give the non-custodial parent the release form. Turbotax will claim the child for EIC and head of household (which always stay with the custodial parent) but will not claim the dependent exemption or child tax credit, which go to the other parent if you give them the release form.
