There are also temporary UPNs, allocated when a school receives a pupil who is likely already to have a UPN, but the school is not told what that UPN is.
Ceir hefyd RhUDau dros dro, a ddyrennir pan fydd ysgol yn derbyn disgybl sydd â RhUD yn barod fwy na thebyg, ond nad yw'r ysgol wedi cael gwybod beth yw'r RhUD.