OK, let's back this up a bit because there is information missing and it's really hard to play 20 questions. Here's what I suspect has happened. Correct me if I'm wrong.
You have a subsidized tenant from whom you have collected a security deposit. The support agency has been paying their share of the tenant's monthly rent, but the tenant has not paid their share for the past two months. The tenant has moved out and breeched their lease, which has five months to go. Even deducting the tenant's share of rent that is in arrears from the security deposit up to the date of breech, there is still $1,500 left over.
In order to better understand the situation and give you more meaningful answers I need the following information: (Humor me - there is a method to my madness.) I don't necessarily see a need to make a refund but need more information to be sure.
1. How much is the security deposit?
2. Who paid the security deposit, the tenant or the support agency?
3. How much is the rent?
4. How much does the tenant pay?
5. How much does the support agency pay?
6. Specifically, what was the last month the tenant paid for?
7. Specifically, what was the last month the support agency paid for?
8. What was the dollar amount of any damage the tenant did that needs to be deducted from the security deposit?
9. What date does the lease expire on?
10. What date did the tenant move out?
11. What date did the tenant notify you they were breeching the lease?
12. What date did the tenant surrender the keys to you?

