In this video:

To remove a contract from the planning you can: 

• Delete it
  • From the 'planning' screen: right-click on the contract and choose 'delete'
    

• From the 'contracts' screen: click on the trash bin icon next to the contract
  
• Change the status to cancelled
  • Open the contract, go to the reservation tile, look for 'status' and change the status to 'cancelled'. This way you can keep track of this contract's data.