The formula that actually matters
True BMV isn't "advertised value minus asking price." It's realistic current market value, minus purchase price, minus every cost of getting the property into a sellable or lettable state. A property advertised at £180,000 against a claimed £220,000 value isn't necessarily £40,000 below market — if it needs £25,000 of work and £8,000 of transaction costs, the real discount is under £7,000.
Start with the market value, not the discount claim
Never take a seller's, agent's, or algorithm's stated "market value" as given. Establish it independently first, from genuinely comparable sold prices — not asking prices, not "similar" current listings, not an optimistic estimate. This is the step most BMV claims skip, and it's the one that actually determines whether a deal is real.
Then deduct everything, not just the obvious costs
Stamp Duty Land Tax (including the additional-property surcharge if applicable), solicitor and lender fees, survey costs, refurbishment with a genuine 10–15% contingency, finance costs for the period you're paying interest before the property earns, council tax and utilities during any works, and eventual selling or refinancing costs if that's part of the plan. Skipping even two or three of these is how a "great deal" turns into a break-even one.
How PropertyAlert applies this
This is the same discipline behind PropertyAlert's investment score: every listing's discount is measured against real postcode-sector Land Registry benchmarks, not the asking price framing on the portal. A high investment score reflects a genuine gap to comparable sold value — it doesn't yet account for your specific refurbishment or finance costs, which is exactly why this manual step still matters even on a well-scored listing.
The discipline that separates real investors from bad deals
Run this calculation before you view a property, not after you've fallen for it. If the true BMV after every deduction is thin or negative, walk away regardless of how the headline discount was marketed — there will be another listing.