Dying without leaving a will is not a good idea.
If you haven't made a will, then when you die, everything you own will be shared out according to the law instead of in accordance with your wishes. This could mean your estate passes to someone you hadn't intended - or that someone you want to pass things on to ends up with nothing. For example, if you're not married and not in a civil partnership, your partner is not legally entitled to anything when you die. If you're married, your husband or wife might inherit most or all of your estate and your children might not get anything (except in Scotland). This is true even if you're separated. If you have children or grandchildren, how much they are legally entitled to will depend on where you live in the UK. All of this can be avoided if you make a will, setting out your wishes.