The huge mistake tens of thousands of people make every year which can cost £5,000 or more to fix
![The huge mistake tens of thousands of people make every year which can cost £5,000 or more to fix](https://i2-prod.walesonline.co.uk/news/uk-news/article29588919.ece/ALTERNATES/s615/1_18.jpg)
It can be a moment of madness or confusion, but the consequences can be very expensive indeed - this is how you'll know if it happens to you and what you should do about it