What's the worst clerical error you've seen?

[FrodoSwaggins]

There's a Reddit post making the rounds about someone who missed out on a full ride college scholarship because their brother stole the acceptance letter as a "prank." (Brother is a psycho, take him to court!)
What are some of the worst clerical errors you've seen? How did they impact people?
I'll go first: maybe not technically an error. At one point, I achieved the American dream briefly, getting hired as a temp and then using that position to move into full time. When I took parental leave, the weekly pay was going to be driven WAY down by the weeks of temp work hourly pay driving down my annual average. It was so much money, I actually delayed the leave to an almost silly amount in order to max out the benefit. It was embarrassing and I feel like if I had talked to someone with a brain overseeing that program, they maybe could have sorted something out.