Rental Agreement Cancellation Contract

[Kenny Stone]

Good morning!

I have tenants that are wanting to move out before their lease is up. I have it stated in the contract that to have the lease agreement cancelled (prior to the agreed upon end date) there are two stipulations. 

1) Forfeit of the entire security deposit 
2) The tenant agrees to pay the sum equal to (2) full months upon moving out

Now the tenants agreed to these stipulations when they signed the original lease and they agreed again when they let me know they would like to be let out from the lease. We talked through the exact bullet point in their copy of the lease. 

Does anyone know of a good example of a contract I could have them sign to keep the pressure on them to make the payments? 

Is it really as simple as __________ agrees to pay $___ to landlord for cancellation of lease agreement? If anyone has any experience with this type of paperwork, I would appreciate any/all feedback!