Stamp perforations are intended to place the printed design neatly and centrally within the perforation lines. Incorrect machine settings, misfed paper, creasing or folding can nevertheless produce a variety of perforation errors.

The most common variety is misperforation, including perforation through the design. In such cases, both the printed design and the perforations may be normal in themselves, but their positions relative to one another are incorrect, leaving the design off-centre. Minor misperforation is usually considered an aesthetic defect, and on some early issues it is so common that well-centred examples are actually scarcer and more desirable. Major misperforation, however, can be a significant philatelic variety, especially when the perforations cut into the design or expose part of the neighbouring stamp or the frame of a souvenir sheet.

Faulty operation of the perforating machine, or creasing and folding of the paper, can also produce much more complex perforation abnormalities. Large and visually striking examples are generally rare and particularly interesting to collectors.