Corporate client makes businessman work 2 months of unpaid overtime, pay large invoice he sends by mistake 1 year later: 'The worst working experience of my life'

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Ally Perry • Writer and Editor
Dec 9, 2025 9:00 PM EST

Not all customers are created equal, and those who work for them should react accordingly.

Some people or companies are an absolute dream to collaborate with, the kind of experience that gives the motivation to keep going even when everything else seems to be less than perfect. Others seem to have been summoned directly from the underworld to give everyone around them the kind of unbearably hard time that makes somebody never want to talk to another human being ever again.

The hardest part about those clients that fall into the latter category is that most of the time, the best that can be done is to wait things out until they leave you alone and try not to go insane in the meantime. It is a rare opportunity that justice can be served in these scenarios, which means that it can be tempting even if it doesn't abide by workplace rules.

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  • a businessman sat by an open laptop in a bright office smiles as he receives an email on his phone
    via Getty Image (Unsplash+)

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

  • One man found himself in an enviable situation after a very difficult client made a mistake that he profited from. A year earlier, he had worked with them on a project that turned out to be a traumatizing experience because of the way that they handled it. He also had to work for them for two extra months, for which he wasn't reimbursed.

    A couple of months ago, he was writing up an invoice for a new client, which he accidentally sent to the one from last year in a sleep-deprived state. To his surprise, they paid the invoice without questioning it, leaving him with a sizeable sum of money. After the awful time he had had, he made the decision to keep it.

  • Accidentally sent a huge invoice to a nightmare client for work I didn't do. They paid it, and I'm keeping the money

    About a year ago, I had a corporate client that was easily the worst working experience of my life. Extremely rude, treated me like shit, constantly calling me during non-work hours. They always demanded I do more outside the scope of the contract. I eventually managed to miraculously meet all their requirements and finished the job, even though it went 2 months over schedule (which I never got paid for)
    via Jumpy_Inspector_6972
  • So a few months ago, I flew back home after completing a project for a new client. I was totally sleep deprived but just wanted to get things wrapped up. Typed up the typical thank you email, attached the final invoice, hit send, and crashed for the night.
    via Jumpy_Inspector_6972
  • Woke up the next day and checked my phone. Saw a notification from my bank about a deposit, and another auto-email I get when an invoice is marked paid. Then I saw a third email from the new client I just finished with. I opened that, and it basically said Hey, loved the work, just send over the invoice when you can so we can get you paid.
    via Jumpy_Inspector_6972
  • view from behind of a businessman on the phone as he looks at his email inbox
    via Curated Lifestyle (Unsplash+)

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

  • I was so confused while reading through it. I thought I literally just sent them the invoice last night??? I didn't think I had any other outstanding payments.
    via Jumpy_Inspector_6972
  • I closed that email and went back to check the payment confirmation. That's when it hit me. The payer name was the disastrous corporate client I worked with last year. I must have autofilled the wrong email address in my sleep deprived state, as the first three letters are the
    via Jumpy_Inspector_6972
  • same. But regardless, their accounts payable must be such a disorganized mess that they didn't even check if the invoice was valid, they just paid it. It was a large sum as well. That should tell you a lot about just how disastrous this client is.
    via Jumpy_Inspector_6972
  • After thinking it through, I decided to use that to my advantage, because fuck them. I took the money and set it aside into a safe investment account, just in case they ask for it back. But at this point it's been months, and I haven't heard anything from them. I plan on keeping the money in the account for a year. But I am not going to be proactive in giving it back. Considering all the unpaid overtime from last year, I'm calling us even.
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  • tldr; Accidentally sent a large invoice to an abusive client I haven't worked with in a year instead of my new client. They paid it without checking. I'm keeping the money as back pay for the hell and unpaid overtime they put me through.
    via Jumpy_Inspector_6972
  • the arms of two different people lean across a table, as they pass documents and invoices to one another
    via Behnam Norouzi (Unsplash+)

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

  • westsideriderz15 ASA: add service agreement. I drop that after a certain point with troublesome clients. "Sure, I can provide a proposal for that additional work..."
    via westsideriderz15
  • OP Jumpy_Inspector_6972 Yup, learned my lesson the hard way. Now I make sure to be super specific in the agreement so they can't take advantage of vague wording to get free work. >"Sure, I can provide a proposal for that additional work..." This is super important. I've had clients try to push for verbal agreements, giving excuses like oh I'm too busy to check email/stop by office right now to sign off, or don't worry, we spoke on it, you have my word. Yeah right
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  • Traditional-Ad-1605 I would say that if the amount was large enough (say >$50k) it will be flagged for review by their auditors. The questions will come, it will lead them to discover the error, demand refund, and overall create an awkward state of affairs. While you may have already decided that you won't work with them again, as a small business, you do want to maintain your reputation, because you can't control who they speak with and the narrative that will result.
    via Traditional-Ad-1605
  • OP Jumpy_Inspector_6972 Their year end is approaching, so if they catch it in the audit, I'm expecting it would be sometime within the next few weeks. Also you bring up a good point about reputation, which I didn't even consider. They are large enough to have numerous connections. But honestly, I'm pretty done with this industry, so at this point, whatever happens, happens.
    via Jumpy_Inspector_6972
  • igottogotobed Things on the internet I don't believe. A nightmare client would never pay an invoice without reviewing it, but cool fantasy.
    via igottogotobed
  • OP Jumpy_Inspector_6972 It's a large corporate client. So you're overlooking the fact that AP is a completely different department. The only explanation I can think of is that I was already in their system, so they negligently auto-approved it
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  • TR6lover Within 24 hours! I'd love clients like that!
    via TR6lover
  • OP Jumpy_Inspector_6972 Same, which is part of the reason why Im done with this shit. With large clients, you get lucky maybe like 5% of the time. Small - mid size clients though, they are a blessing.
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  • XFancyPuddingX If they let's sayyyyy they do an internal audit and catch this payment. You are royally screwed, you can't even play this off as a mistake because you have purposely set aside that exact ammount, you caught your blunder but didn't try to correct it. The right thing to do would of been to do a refund, explain the mistake, then re do the payment and send it to the new client for them to pay for. Did the new client not ask why they didn't have to pay???? Any sane person would be aski
    via XFancyPuddingX
  • OP Jumpy_Inspector_6972 Not really. Which is why the money is sitting in another account, collecting interest, but has otherwise remained untouched. >The right thing to do would of been to do a refund, explain the mistake, then re do the payment and send it to the new client for them to pay for. Did the new client not ask why they didn't have to pay???? Any sane person would be asking that so unless you also took another payment from them covering this up is just as hard as not so it makes no se
    via Jumpy_Inspector_6972
  • princessstrawberry Sounds to me like you billed them for all that overtime, and they paid it.
    via princessstrawberry
  • Oat Musee Exactly. Having that extra layer of protection with an ASA is such a smart move, especially with clients who love to blur boundaries. Sets the tone that your time and effort come with limits and expectations.
    via OatMusee

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