Deductions & credits

The custodial parent who doesn't claim a tax exemption for a child can claim the dependent care credit if that parent meets all the following conditions:
- You are the custodial parent
- The child was under the age of 13 or was physically or mentally unable to care for himself or herself
The noncustodial parent is entitled to claim the child as a tax dependent

If you meet all the above conditions, then set him up as a non-dependent in the Personal Info section.  It should say Nondependent - for EIC/dependent care only to the right of his name. 

Go to Deductions & Credits, and answer the questions accordingly.