Understand how your property valuation is estimated

Every key figure in a Property Market Data report says where it came from, and when wherever a date exists. This page explains the records we use, what the labels mean and what the data cannot tell you.

This is an estimate from comparable sales, not a RICS or mortgage valuation, and not a survey.

What we use

Sold prices. HM Land Registry Price Paid Data: the price and date of home sales in England and Wales. It is published with a delay, so the most recent sales may not be in a report.
Floor area, age and energy rating. Energy performance certificates. A certificate can be older than an extension or a refit.
Prices over time. The UK House Price Index, published by HM Land Registry and the Office for National Statistics. We use it to restate older sales to today's prices.
Risks and designations. The Environment Agency flood map, Historic England's list of listed buildings, conservation area records and council planning records.
The area around a home. Public data from the Department for Education, Ofsted, Ofcom and the police: schools, broadband and recorded crime.
The market now. Homes on the market that we track, with their asking prices and how long they have been listed. This is listing data, not official data, and it does not cover every home.
Licensed data. Some of the records we use come from licensed commercial sources. The report's table of key figures says what kind of source each figure comes from.
What you tell us. Your answers about the home, labelled Given. Where a record exists, the report shows it beside your answer and says whether they match.

How each key figure is labelled

Observed.: Read from an official record or service. Example: the floor area on your energy certificate.
Given.: Told to us by you and not checked. Example: the floor area you enter when we find no certificate.
Derived.: Calculated from records by a rule we state. Example: a sold price restated to today with the house price index.
Modelled.: Our own estimate, from data and assumptions. Example: the estimate itself, and the adjustment for the local market.
Not known.: We looked and could not find it. We never treat it as zero. Example: a floor area, when there is no certificate and you have not told us.

From data to an estimate

Find the sales nearest to your home in place and size.
Restate older sales to today's prices with the official index.
Where we know your home's size, scale each close sale to it.
Adjust for what you tell us, within limits, and show every adjustment with its reason.
Set a likely range and a confidence reading, and say what could change them.

What the data cannot tell you

Nobody visits your home. We cannot see its condition, its light, its view or its layout unless you tell us.
Sold prices arrive late. HM Land Registry publishes sales with a delay, so the most recent sales may not be included.
Some homes have no sale in the records we hold. For those, the report says there is no recorded sale.
Records can be out of date. A certificate or a register entry can come before an extension, a conversion or a change of lease.
Floor area is missing for some homes. Where there is no certificate, we ask you, and the report says how sure it is.
A search that finds nothing is not proof. Councils supply planning records, and some have not supplied every one.
Flood information covers rivers and the sea, not surface water.
School, broadband and crime figures describe the area around the postcode, not your address.
Where few homes have sold nearby, the range is wider and the confidence reading is lower.

Software-written paragraphs

Some paragraphs in a report are written by software from the report's own figures. The figures themselves, the ranges and the lists of sales are calculated, not written.

If something is wrong

If a fact about your home is wrong, tell us at admin@propertymarketdata.co.uk with your order reference. We will look at it and tell you what we find. We do not change a report quietly.

Value My Home

Where the data comes from

Energy performance certificate data: contains public sector information licensed under the Open Government Licence v3.0. Contains Royal Mail data © Royal Mail copyright and database right 2026. Source: Department for Levelling Up, Housing and Communities.