For many couples, the decision to live together is usually a happy experience and an important phase in their lives.
David and Emily are buying a house together but aren't getting married
But statistics suggest that more than half still think they have the same rights as married couples.
In fact, no matter how long you've been living together, cohabiting partners have fewer rights than married couples over a range of crucial issues, such as access to children, property and inheritance.
Now couples are being asked to consider making a pre-nuptial agreement - which they can do using an on-line form.
We found out more about your rights with family lawyer Miranda Green and one couple who are living together, David Mills and Emily Sollis
The new agreement will be available from the website advicenow.org.uk and you can find a link to that site at the right of this page
The website has won an award from the Plain English Campaign and should be useful for Britain's four million cohabiting couples, and the agreement claims to protect from any eventuality.
Remember, if you have any concerns over your legal position, you should consult a solicitor or visit your local Citizens' Advice Bureau
One of the things couples who are considering living together are advised to do is to list all their possessions saying who owns what.
This makes it a lot easier to divide things if a relationship ends and arguments over possessions are one of the main reasons why couples land up in court.
A recent survey - for Website AdviceNow - found that:
65.4% of women wrongly believe that they have the legal right to financial support from their partner if they have been living together over five years.
77.4% of people wrongly believe that the father of a child automatically has a right to make decisions about his child's future, regardless of whether or not he is married.
47.9% of respondents wrongly believe that if one of a cohabiting couple of over five years died without making a will, the surviving partner would automatically inherit what was left behind.
In fact, the Queen is more likely to inherit than the partner.
A copy of the Living Together Agreement is available to download from Advicenow.org