The credit does not stack on top of the dependent care benefit. The credit is available on the first $3000 of expenses for one child and $6000 for two or more children, but any workplace benefit reduces that limit. Because you had $5000 of workplace benefits, you could use $1000 of the care cost toward the credit if you were paying for 2 children, but if you only have 1 child, you have used up the $3000 eligibility for the credit.
Note that the workplace benefit is much better financially than the credit, for anyone whose income is more than $35,000.
