The CO code holder must report on all ten thousands-blocks regardless of whether a thousands-block is assigned to, or not retained by, the reporting service provider. If the CO code holder has donated a thousands-block, then an “X” must be indicated in the “Donated to Pool” column on the U1 form. If you do not report on all ten thousands-blocks, the CO code (NPA-NXX) will remain on the UMR.