Be careful with the default smearing method (ISMEAR=1)
The default for ISMEAR is 1 in VASP. This setting is not appropriate for insulators and semiconductors, and can results in one-electron occupancies that are larger than 1 (2 for non spinpolarized) systems, and conversely some states being occupied by less than 1 electron close to the Fermi-level. It is strongly recommended to set ISMEAR=0 in the INCAR file and use a small width SIGMA=0.05 (do not make SIGMA too small, values below 0.001 can also lead to undesirable symmetry breaking).