Marriage Value is a term that describes the increase in property value once you extend the lease. One of the best reasons for people to extend a lease is that doing so can make your property increase in value overnight. So if a £200,000 flat increases in value to a £250,000 flat, the marriage value is £50,000.  This is so important in lease extensions because if you extend the terms of a lease that has less than 80 years remaining, you'll have to pay some of that marriage value to your freeholder. Usually, this is about 50% of the marriage value, on top of your previous lease extension premium.  This means that extending your lease at this time is super expensive. So, in the previous example, you'll have to pay an extra £25,000 on top of the premium to get a lease extension if you did it with less than 80 years on your term.