I got a £1,300 fine! (Refusing to paying off a government mistake)

If you are speeding, you are in the wrong, you pay a fine, if you have stolen from a shop, you are in the wrong, you pay a fine, if you break something expensive in a shop, you are in the wrong, you pay a fine.  If the government makes does something wrong, such as overpay you, they FINE you. you shouldn't have to pay for their mistake.

They disguise it as a payment, but the definition of fine is: "punish (someone) for an illegal or illicit act by making them pay a sum of money.". The problem is, they are the one who committed an illicit act, and they punish you rather than themselves.

So in 2012, HM revenue and customs (the UK's customs/tax department) sent my parents a letter saying they were going to pay my parents £1,300 in child tax credits. £1,300 might seem quite high for some of you, but my parents income (joint) is under £20k. Today, 2 years later, they are saying they overpaid us £1,300. WHAT?! They are basically saying my parents should have got no tax credits—something's wrong there; even families earning £40-70k get some tax credit.

Also, the expect the payment by the 21st of next month. None-the-less, my dad refuses to pay it, although even if he planned to, it would be impossible to. My mum and dad together have under £300 every month after bills, the mortgage, and everything else is paid for, so if we were going to pay it back it would take at least 5 months.

Long story short: The government are charging my family £1,300 (to pay in one month) for their mistake and we aren't paying it =)