Diagnosis
You have tried to manually insert a contract-based 'acquisition'stamp tax condition for the contract.

System Response
It is only possible to create object-based 'acquisition' stamp taxcondition. For each assigned object, a separate 'acquisition' stamp taxcondition has to be created.

Procedure
You can manually select one of the assigned objects of the contract as acalculation object for the condition.
If you save or refresh the contract, the system will automaticallycreate the missing conditions for the objects for which the stamp taxcondition has not been created yet.