15+ Employees who made expensive mistakes: 'My coworker hit reply-all on an email... the silence in the office was so loud'

Author image for Remy Millisky
Remy Millisky • Writer and Editor
Mar 6, 2026 3:00 PM EST

Make a big enough mistake and it'll cost you your entire career! Just ask these workers, who witnessed as it happened in real time. 

Making mistakes on the job happens to everyone now and then. We all wake up bleary-eyed every day and start working like, an hour after that. It's bound to happen! 

Some jobs allow workers to make mistake after mistake as part of a learning process. But other jobs have zero room for error! And even a single mishap can cost the company a small fortune. 

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    Group of 3 coworkers react with shock over a mistake they've made.
    via Nappy

    Group of 3 coworkers react with shock over a mistake they've made. 

    The image does not depict the actual subjects of the story. Subjects are models.

  • Can you recall your biggest mistake ever? Maybe you accidentally sent out the wrong invoice and significantly undercharged a client. Perhaps you were entrusted to care for an expensive electronic, only to break it and watch your colleagues react in horror. 

    There are many such ways that a person could accidentally, in a moment, torch their entire career (or at least make their boss fuming mad). For example, some people cost themselves 6 figure jobs just by sending a snarky email or instant message to the wrong person! 

    These stories shared below are some of the most expensive mistakes a person can make. Some had actual monetary values on the incidents — like, imagine knowing that you cost a multi-billion dollar company an entire day's worth of work! Or imagine accidentally breaking a peice of hardware that costs tens of thousands of dollars. It can happen to anyone who isn't very, very careful! 

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    Here's how to make a loud exit

    Cheezburger Image 10612148224
    via Flashy_Baby7022
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    What’s the most expensive mistake you’ve watched someone make in real time?

    Visual_Rice_4381 I once hooked up a voltage regulator wrong on an aircraft carrier's electrical generator. Watched as nearly $250,000 in tax payer money went up in a tiny blue puff of smoke.
    via Visual_Rice_4381
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    Ruining a legacy

    OkCastor I was the accountant for a small, but very profitable family business. Been there from the beginning and the owner started to integrate his dumba son into the business as he was about to retire.
    via OkCastor
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    In two years, the son turned the lucrative business into a dumpster fire and ended up selling it to a competitor as he was burned out and wanted to "find himself". It was heartbreaking to see the disappointment in the father's face when he had to sign the sale agreements.
    via OkCastor
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    Employee explains a mistake to 2 colleagues who listen closely.
    via Getty Images

    Employee explains a mistake to 2 colleagues who listen closely.

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    Breathtakingly bad situation here

    zerbey Had a customer call because his restore wasn't working. Many years worth of data. Turned out he had never backed anything up, just a pointer to the two very important directories. You'd think he would have wondered why his backups completed in seconds instead of what should have been hours. You'd think at
    via zerbey
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    some point he'd have done a DR test, but nope. Anyway after a few minutes of fruitless troubleshooting his manager came on the phone and asked me to summarize what happened. Then he said "OK he's fired, thank you very much you can close the ticket". So, lost his job and multiple terabytes of company data all in one day.
    via zerbey

    Maybe that was the right choice! It's either fire this fellow, or have him return to all his coworkers, take a deep breath, and tell them face-to-face that all their data is lost forever. 

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    Not this!

    fertdingo I saw someone accidentally trip a dry chemical fire extinguisher on a newly installed 5 million dollar emergency gas turbine generator for a power plant.
    via fertdingo

    At least it worked? 

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    Grokent I watched a guy delete his SSL certificate that was hardcoded into the firmware of like a billion dollars worth of networking equipment. I told him not to do it until he was ready to deploy the new certificate. The screen prompted him twice telling him he wouldn't be able to undo it. He did it anyway.
    via Grokent
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    He then threatened to sue me personally when he realized he had 48 hours to deploy an updated certificate across dozens of different products before they became non-functional.
    via Grokent
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    What was bro thinking?

    JimTheJerseyGuy Watched an electrical contractor in a data center trip the emergency power off button while trying to exit the building for a smoke because he thought it was the switch to disengage the mag locks on the door leading outside.
    via JimTheJerseyGuy
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    The EPO was clearly marked and under a plastic safety cover that had to be physically lifted up and the RFID card reader that would unlock the door was right there as well. His own company had installed said items just a week or two before, too.
    via JimTheJerseyGuy
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    Took down hundreds of production servers along with cascading effects across the organization. I don't know the exact dollar figure but a multibillion dollar company shut down for a solid business day as a result.
    via JimTheJerseyGuy
  • 15

    Careful who you instant message about... those messages really are instantaneous

    fzcwhnu Watching someone send a message about a coworker... directly to that coworker
    via fzcwhnu

    Even if the jab wasn't that bad, it can still set people on edge to know that their colleagues are talking about them behind their backs. 

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    Livexwired A dude I used to work with really hated me for whatever his reasons are. During co id I sold my car for a profit and took the money and upgraded to a much nicer car. A week later he did the same without consulting his recently married wife.
    via Livexwired
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    3 days later he had a social media post up about how he returned the car, wasn't able to get his down payment back, and how he doesn't need materialistic possessions for validation, etc. I asked him how the new car was the next day and watched his forehead vein pulsate.
    via Livexwired
  • 18

    Gasp!

    spotolux Worked in the warehouse of a silicon wafer brokerage. One of my coworkers was putting a pallet of wafers up on the top of a 4 level rack, like in home depot. The pallet wasn't straight and caught the pallet next to it.
    via spotolux
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    The guy tried to pull back but that made it worse. Before any of us could react the pallet he'd snagged tipped and fell through the rack to the pallet below, triggering a chain reaction resulting in 12 pallets falling. 10s of millions of dollars worth of inventory lost.
    via spotolux
  • 20
    Shockwave2309 My colleague was teaching an industrial robot to handle stuff in and out of a 1M€ tool. After nearly 10 hours of teaching I came up to him to tell him it's time to leave. He proceeded to "bring the robot to a safe position", mixed up Z- and Z+ (directions in the robot) and completely crashed into the tool.
    via Shockwave2309
  • 21
    Tool needed repairs close to 300k€, the handler needed repairs close to 150k€ and his working hours of the last two weeks were useless (maybe 50k€?) On another occasion I was done teaching a robot, gave controls to the (authorized) customer who immediately crashed the robot... 200k€ damages all in all lol
    via Shockwave2309
  • 22

    Uh... you're telling me you can't use a wet wipe on a laptop?

    Big_Raspberry_2... watched my roommate try to clean her laptop keyboard with a wet wipe and fry the whole thing.. $1200 gone in like 10 seconds.
    via Big_Raspberry_2711

    Skill issue, to be so honest. A laptop can handle a little bit of water if you are pure of heart. 

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    Cheezburger Image 10612147200
    via beaushaw
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    cut into those spots. The owner did this with with every contractor who was working there. He was on one side of the room hanging his drywall and there was another guy working on the other side of the room. The other guy said "Oh, sh "so he turned around the the guy had cut a big opening in a wall. In the
    via beaushaw
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    Cheezburger Image 10612146432
    via beaushaw
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    Cheezburger Image 10612145408
    via peteyshabby
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    Cheezburger Image 10612146944
    via rcowie
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    Cheezburger Image 10612145920
    via rcowie
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    Now that is an expensive mistake!

    Cheezburger Image 10612145664
    via Master-CylinderPants
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    Cheezburger Image 10612146176
    via 1976warrior
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    Cheezburger Image 10612147456
    via 1976warrior
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    Bye bye new cabinets

    Cheezburger Image 10612147968
    via Emergency-Pack-5497

    Construction always does take longer than you expect it will. 

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    Cannibustible I watched a guy completely destroy a large co-gen system. I was just there to open doors. Don't know what he did, but there was an arc flash and a fire started as he said "Oh f ! Get the f out of here!" About 500k in damages
    via Cannibustible
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    via Cannibustible
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    Cheezburger Image 10612148992
    via Whylslt27
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    via Whylslt27
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    Employee at desk explains mistake she made.
    via Julio Lopez

    Employee at desk explains mistake she made. 

    The image does not depict the actual subjects of the story. Subjects are models.

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