When rotations and reflections are not considered to be distinct shapes, there are 1,285 different free nonominoes.
[2] The 1,285 free nonominoes can be classified according to their symmetry groups:[2]
[3][4] Therefore a complete set cannot be packed into a rectangle and not all nonominoes have tilings.
Two additional nonominoes admit tilings, but satisfy neither of the previous criteria.
[5] This is the lowest order of polyomino for which such exceptions exist.