Martin Lewis has issued a warning to couples up and down the country as he encouraged families to have "unpleasant" chats about finances.
The MoneySavingExpert founder explained how you have no control over where your assets go after you die unless you have a will in place.
Under current rules in England and Wales - known as intestacy rules - if you are married or in a civil partnership, you don't have a will, and your estate is worth less than £270,000, then everything would automatically go to your spouse.
If the estate is worth more than £270,000 and there are children involved, the spouse would inherit half of the remaining assets and the other half would be divided equally between the children.
The rules are different in Scotland and Northern Ireland.
However, if you make a legal will you can decide exactly who and how much of your assets go to who after you have passed.
Speaking during the latest Martin Lewis Money Show Live broadcast on ITV on Tuesday evening, Martin explained: “If you die without a will, it is the state - not you - who decides where your assets go.
“It’s called the intestacy rules and they are complex and they vary by UK nations.”
Martin went on to explain how it is “especially important” to consider a will if you’re not married or in a civil partnership.
He said: “If you’re cohabiting and you’ve lived together for 20 years and you’ve got 17 children - that doesn’t matter in the eyes of the law.
“You would not get anything without a will. So it’s even more important in those situations.
“I’d also suggest you consider a cohabitation agreement of what happens if you were to split up if you’re not married.”
Martin recommended getting a gold standard solicitor-drafted will - and there are ways to cut the cost of this.
Free Wills Month takes place every March and October for those aged 55 and over.
The service is free, on the hope that you will leave something to charity - the typical donating is around £300 but it is up to you.
Hundreds of solicitor firms across the UK normally take part, though different areas participate in different months.
You can see the full list of participating areas by typing in your postcode here.
