Is it mandatory to request a derogation in ALL new proposals, in case the Partner wants to use the simplified cost method for field office costs?

Yes. Since article 8.2 h) of the General Conditions recognise as eligible “only the portion of the costs (of field offices) which corresponds to the rate of actual use of the infrastructure for the purposes of the Action”.

If the Partner wants to apply a simplified cost allocation method, it needs to request a specific derogation in section 11 of the Single Form for all new proposals (in case, a Modification Request can be submitted for ongoing Actions).