See also: letters from the DWP. Specifically tax credits. I know a few people who were overpaid tax credits - (weren't most people!) and when they were stopped and they were still owing, they had to pay them back at say £40 a month or £60 a month until the amount was cleared.
Although they paid on time every month - by direct debit - they still got nasty snotty harsh RED letters saying 'you have not paid your monthly installment, and so now the £639.00 you owe has been passed to a debt agency, and you have lost the right to pay in installments!'
They had paid! They called the DWP, and after an hour of waiting on the line, they got told 'oh yeah loads of people have been getting them, just ignore it. We have received your £60 don't worry about it!'
A mistake, that caused the person loads of worry and stress and wasted time on the telephone when it was a mistake. One woman I know who owed £975 and was paying in installments over 18 months, got FOUR of these shitty letters in 8 months.
Computer generated my fucking arse.
It's human error. Someone has to get the bloody computer to do it, and it needs printing out and putting into an envelope - and posting! Them blaming the computer does my head in!