An unauthorised, unplanned or unarranged overdraft happens when a payment takes you into overdraft without previously being agreed with the bank in the UK.
There are actually a scary number of ways this can happen.
Fortunately, this awesome infographic goes over everything you need to know to spot them and combat them.
Pay special attention to little fees like this, because they will add up over time. And banks are notorious for charges like this.
Provided by Sunny Loans