... particularly if you deposit cheques in the automated machine thingy.
You know the one that bank staff encourage and cajole their customers to use as it means you will have less of a wait [and they do not have to employ so many actual people/counter staff].
Bloody Barclays. This has happened to me TWICE now. I usually use the counters to deposit cheques as I have previously had cheques to the value of £300 go missing and not credited to my account when I dropped them in the machine. Luckily I had a receipt and was able to prove that I had deposited the cheques... but it took Barclays forever to investigate and they were so blasé and non-apologetic 
Now I have found it has happened again. Against my better judgement I deposited £400 worth of cheques in the automated machine about 2 months ago. I was in a rush, the queue was immense, I thought what's the chances of my cheques going missing again? Well, it appears that they have. I have just found the receipt tucked in my diary and thought I would check my statements to ensure it has actually been paid in... to discover I can't find it anywhere on any statement. Ring telephone banking, chap on the other end also can't find it anywhere. Has passed it on to the complaint team, will take 48 hours for them to investigate apparently.
I tell the telephone banking guy I want to make a complaint. He has given me a generic Barclays address to complain to. No thanks, I want a real person, preferably someone with authority to hear my story. Does anyone know who I should take my complaint to?
I am feeling mighty pissed off but also rather concerned as some branches are now fully automated, i.e. no counter staff just machines. These sort of mistakes are completely unacceptable imo. Yes, I probably should have checked my receipt earlier but in the general busyness of life it just got overlooked. It is also possible that my receipt might have gotten lost and then I would have struggled to prove I even deposited money into the machine! I have quite a few clients who pay me via cheque and I am now wondering if I need to tell them that I no longer accept this method of payment.
So please everyone, look after your receipts for depositing cheques and also make sure your money has actually been deposited into your account!