When to use it
Use it when you've made a mistake, big or small. Own it in one sentence and go straight to the fix. People mainly want to know it's being handled; repeated apologies make it about your feelings instead of the solution.
Example
Manager: “The invoice went to the wrong client.”
You: “I missed that. Here's how I'm fixing it: I've emailed both clients and the correct invoice goes out today.”
In an email or Slack message
By email: “I made an error: the invoice went to the wrong client. I've contacted both and the corrected invoice is going out today.” Short and specific builds confidence.