If all parties have fulfilled their obligations as per the terms of the agreement, they can mutually decide to conclude the agreement.
To finalize an agreement:
Go to the Agreement page.
Click on "Signal Agreement's end" to start the process.
Once all parties have signed off on the finalization, they will be able to withdraw their collateral deposited at the start of the agreement. To do this, simply click "Withdraw from Agreement" when it's available.