うっかりミス

noun

careless mistake; honest mistake; slip-up

A mistake made through inattention or absent-mindedness, not through malice or incompetence. Often used when someone forgets something, overlooks a detail, or makes a simple error.

• うっかりミスで書しょ類るいを間ま違ちがえて送おくってしまった。

  I accidentally sent the wrong document due to a careless mistake.

• うっかりミスを防ふせぐために