Methodology

How FirstBid calculates property variance

A FirstBid report is only as good as its weakest match. This page sets out exactly how we retrieve records, decide whether a record really belongs to your property, and what we refuse to do with evidence that does not meet the bar.

The pipeline, stage by stage

Stage 01

Capture the listing as claims

The listing is parsed into a structured record of what the seller is asserting: asking price, tenure, property type, bedrooms, floor area, council tax, and any statements about condition, extensions or risk. Nothing is interpreted at this stage — we are recording the claim exactly as made.

Stage 02

Resolve property identity

Before any property-level record can be used, we establish which property the listing is about. Identity is resolved from a building number or name where one is available, from a registered sale price history that fingerprints a single address, or by narrowing on attributes such as property type and floor area. If none of these resolves to one address, identity stays limited and the report says so.

Stage 03

Retrieve official records in parallel

The postcode is geocoded through ONS data, then the EPC register, HM Land Registry Price Paid data, planning designations, Environment Agency flood data and Police.uk street-level crime are queried independently. Every source returns either data or an explicit reason it could not answer. A source that fails never becomes a silent zero.

Stage 04

Grade and cross-examine

Each retrieved record is graded for confidence, then compared to the corresponding listing claim. A gap between the two is recorded as a variance with both figures and both sources attached.

Stage 05

Write the findings

Every finding is written in four parts: what we found, why it matters, our take, and its negotiation relevance. Findings cite the register they came from and the date the record was retrieved.

Stage 06

Apply the adjustment rule

Only high-confidence, property-level evidence can adjust a financial figure. Area-level context — postcode medians, neighbourhood crime, local price movement — is printed as context and is never allowed to move a number about the property itself.

Evidence confidence tiers

Every piece of evidence in a report carries one of four grades, printed next to the finding it supports.

High confidence

The record is tied to this specific property — by building number or name, by a matching registered price history, or by a unique attribute match. Only evidence at this level is allowed to move a financial figure in the report.

Limited confidence

The record is probably about this property but the match is not conclusive — for example one of two plausible candidates at the postcode. Shown, explained, and never used to adjust a number.

Not verified

The listing makes a claim we could not test against any register. Reported as unverified rather than accepted or rejected.

No record found

The register answered, and it holds nothing for this address. Distinct from a failed lookup, which is reported as an error with the reason.

What we will not do

  • Borrow a neighbour's EPC certificate when we cannot match one to your address. The report says "unable to verify" and explains why.
  • Treat a postcode median as a valuation of a specific property.
  • Deduct ownership costs — service charges, ground rent, running costs — from a property's value. They are costs, and we present them as costs.
  • Present an estimate as a valuation. A valuation is a regulated opinion from a qualified valuer; a FirstBid report is evidence-led research.
  • Fill a gap with a plausible number. A source that fails is reported as failed, with the reason.

Limitations

Public records describe what is on paper. They cannot tell you about condition behind the plaster, title covenants, lease terms, or anything that happens after completion. A FirstBid report is research to inform your offer and your questions — it is not a survey, not a valuation, and not financial or legal advice. You can read the full list of registers we use on the data sources page.

Check a property before you offer

Run any UK postcode through our free lookup for EPC bands, flood exposure, registered sold prices and recorded crime. Got a specific listing? Paste the Rightmove link for the full six-section FirstBid report.