Abstract: The invention includes an assembly including a package and a bag system for collecting a biological fluid, in particular blood. The system may be confined in a sterile fashion in the package. The system may include a fluid collecting bag and a device for sampling the fluid to be collected which includes at least one sampling receptacle associated dissociably with the system. The collecting bag and the sampling receptacle are each provided with an identification tag which includes information making it possible, after dissociation of the receptacle from the bag system, to unequivocally establish that the sampling receptacle and the collecting bag come from the same bag system.