Hi Robert,
I assure you ... Yes you can. What you have to have are two different businesses. On the one hand you have the 'legitimate' business - the newsagent /petrol station etc. The second business is the drugs dealing, or money laundering arm of the drug dealing set up.
I agree with you that the right amount of money is going into the till for the transaction, and the right amount of change is being given. But, and this is the important point, the till receipt indicates a higher amount of money going into the till.
The drug dealers deal in cash (or other goods.)- but cash is the norm. They sell the drugs and collect the cash in. This cash needs to be sent back to the drug barons - usually abroad. This cash though cannot just be paid into any bank - because the bank staff are trained to look out for, and report, suspicious cash amounts. So the drug dealers have to find ways to 'clean' the 'dirty' money. Cleaning is where they make the dirty drugs money appear legitimate.
In the past they have purchased £40,000 cars with cash; then sold the car shortly afterwards for £30,000. The new buyer of the car believes they got a bargain, falling for the 'sob' story given by the seller. But the drugs dealer got an even bigger one ... £30,000 of 'clean' money - his main objective.
When I worked in a High Street bank I reported on a waiter who paid in £10,000 cash each week; he claimed this was from tips. The money involved is, I believe, staggering.
The government recently enhanced the money laundering rules to now include car dealers, jewellers, recruitment companies, estate agents ... the list is long; if you deal in cash you need to make sure you are not included. So the drug dealers are always looking for new ways to 'clean' their 'dirty' money.
So the drug dealers approach a local business and ask them to clean their money for them. In exchange they allow the shop/legitimate business to retain say £10% of the money cleaned. The way the shop cleans the money was highlighted in my previous post.
In the example I gave the figures quoted were, I suspect, conservative. You could have a whole group of shops doing this - each one cleaning £30 - £50k a year. And would a bank suspect an Asian man wishing to send back £20,000 to his family in India/Pakistan. No, of course not, because he is a legitimate business and the reason for sending the money is a perfectly legitimate reason. But when the money gets to Pakistan it is then forwarded onto the drugs baron's.
This example is a superb way (I think) of money laundering, cleaning and layering in particular. If HMRC check the legitimate business's tills everything looks totally correct. And who is going to question a £1 error on a till. Just look at the posts above; no one has come up with an explanation as to why this is an ongoing, frequent, event.
I have supplied one possible explanation. It might not be correct but ...