Wrong Photo Size or Dimensions
Photo size is the most frequently violated rule - and the easiest to get wrong. Australia requires 35–40mm wide and 45–50mm high. But the US wants a square 51×51mm, China uses 33×48mm, Vietnam needs 40×60mm, and Canada requires 50×70mm. Submitting an Australian-sized photo to a Chinese consulate is an automatic rejection. Generic photo services often print a single standard size and call it done.