<i>It is obvious that the costs to the bank are higher with customers who need to be followed up closely to avoid credit losses.</i><p>Why is that obvious?<p>The simple fact is, these days, there isn&#x27;t any follow up. No one is &#x27;followed up closely&#x27; in some expensive human-driven procedure. It&#x27;s all automated. The cost of someone going overdrawn by £10 is pennies.<p>It can&#x27;t be expensive because most banks will give you a free overdraft if you ask. Sometimes even if you don&#x27;t ask. I&#x27;ve had a £1500 overdraft facility on my bank since I opened a student account 18 years ago. Back then I used it a lot without any fees. Now I don&#x27;t use it at all but it&#x27;s still there. If that overdraft cost anything I wouldn&#x27;t have it. The only time you get charged is if you haven&#x27;t planned and set things up ahead of time. I don&#x27;t believe for a second that updating a signed int in a database record saves the bank £25 per infringement, yet that&#x27;s what they charge.