Well when I worked for a major high street bank a couple of years ago, if you didn't usually pay in large sums of money we would definitely enquire where you had got the money from. We wouldn't take you to an interview room and interrogate you, just friendly chat over the counter.
In our Bank we didn't have a 'limit', it depended on who the customer was - i.e a student who never normally pays in come in with �5000 cash, he may arouse suspicion whereas a business man who regularly paid in �10K probably wouldn't.
It's all down to the Money Laundering Regulations. If a customer is found to have been laundering money through his account and the Bank staff haven't reported their suspicions, the member of staff is personally liable for prosecution.



