Should we get married?

[ACubed]

I've tried to search online but I can't seem to find anything conclusive. I live with my partner and our child in a house we own together (with mortgage). Neither of us are really fussed over marriage, but people have been telling us we should get married as otherwise if one of us dies the other would have to pay 40% of the house value as inheritance tax - is this the case?
My mum and dad grudgingly got married in their early sixties for this reason they said, but I just can't seem to find anything online to back it up.
Could anyone point me in the direction of some info?
thanks very much.

I did marry my husband 20 years ago, but mainly because he is a traditional man and wanted us to be married. I was ho-hum on the concept but now I am a fan. So many aspects of our lives, especially with children, have been made easier by virtue of us being legally married.

We did get married in an old church, but by a Unitarian minister who did not mention God during the ceremony so as to not irritate my father, a strong atheist.

I don't have any particularly negative associations with the word "wife", but if one does, couldn't one make up an alternative term and use that instead?