wE did this about two months ago

You are expected to pay to readvertise ( usually one weeks rent) and the lease fee for the new tenant ($15) AND RENT UNTIL THEY FIND A NEW TENANT.

They cannot legally charge you anymore and if you have a good agent or landlord chances are they wont charge you at all the extras....

Our landlord just asked us to pay rent until they found a tenant. The tenant ended up moving in the day after I moved out so it all worked out well

Also So you arent liable for septembers rent etc give them notice now. You can give 60 days notice i think to break a lease anyway therefore you wont be liable to any charges if you give enough notice.....