What is negative equity?
Negative equity is owing more on your mortgage than the property is worth. If you owe £250,000 and the home would sell for £220,000, you are £30,000 in negative equity.
How it happens. Two things cause it, usually together:
Falling house prices. The main driver, and outside your control.
A small deposit. A 5% deposit means a 5% price fall wipes out your equity. A 25% deposit provides a substantial buffer. This is the main reason high loan-to-value lending is regulated more tightly.
Interest-only mortgages compound it, since the balance does not reduce.
New-build premiums can contribute — a new property sometimes sells at a premium that does not survive into the second-hand market.
What it actually means in practice. The critical point: negative equity only crystallises if you sell or need to remortgage. If you can afford the payments and stay put, nothing happens. The lender does not call in the loan because the valuation moved — that is not how residential mortgages work. Many people in negative equity during past downturns simply continued paying and recovered as prices rose.
Where it does cause problems:
Moving house becomes very difficult, since selling leaves a debt you must repay from savings. Some lenders offer negative equity mortgages allowing you to carry the shortfall to a new property, but they are limited and expensive.
Remortgaging to a better rate becomes difficult or impossible, so you may be stuck on the lender's standard variable rate — which is expensive precisely when you can least afford it. This is the most common real harm.
Repossession leaves you liable for the shortfall, which lenders can pursue for years.
What helps: overpaying where your deal permits it, which reduces the balance and rebuilds equity faster; improving the property; and avoiding moving until values recover.
Speak to your lender early if payments become difficult — they have obligations to help.