Doesn't happen in Aus anymore following multiple investigations into banking sector misconduct over past couple of decades. Informal overdrafts are now illegal here for most accounts. But it sure as fuck happened to me too. Multiple times, I still remember it was a $35 fee anytime my balance went below zero. I was just a teenager with undiagnosed ADHD overestimating how much I had left. We didn't have online banking yet, I couldn't just check. And that was a significant part of my pay. Cunts.