A printhead assembly having: at least one printhead integrated circuit having a plurality of ink ejection nozzles; and an ink distribution support mounting the, or each, printhead integrated circuit, the ink distribution support being arranged, in use, to distribute ink to the nozzles, the printhead assembly being arranged to be mounted to a printer at the ink distribution support, wherein the ink distribution support is provided with at least one reference feature, the, or each, reference feature serving to provide information on the location of the nozzles upon mounting of the printhead assembly to the printer.