There are lots of reasons to get married of course, mostly emotional or even spiritual. I have some vague memories of law school when it used to be a reason to get married to get a significant tax allowance.
But romance has hit the heights again in the Inland Revenue and marriage can save significant amounts of inheritance tax. How romantic is that?! It applies to civil partnerships and married couples. It is worth considering especially if you are of a certain age.
The Direct Gov website has more detail but basically the first 325,000 pounds is exempt for all. Married couples and civil partners can effectivelt increase that to 650,000 pounds by transferring to each other upon death. That first transfer is exempt. It is not for people living together.
This can be a very significant saving indeed and in these days of house prices way outstripping the allowances is a relevant consideration.
Maybe we shall see the rise again of marriage for tax reasons. Is that "supporting the institution of marriage" as the government says it wishes to do?