Property Address Deduplication: Same Address, Different Lots and Sales

Choose the unit of observation first

Property address deduplication needs a declared purpose. A stock count may need one row per supported premises; a sales study may need one row per transaction. Merging those tasks can remove legitimate repeat sales or count the same building twice. Decide whether the table represents an address, parcel, dwelling, operating premises or sale event before assigning a unique key.

Normalise spelling without assuming identity

Street abbreviations, typographical errors and unit-number formats can create apparent duplicates. Store the original text alongside a normalised form. Use a stable property or parcel identifier where available, then check the relationship rather than trusting string similarity alone. Two records sharing a street number can still refer to different dwellings or lots.

Track subdivision through time

A parent parcel can later become multiple lots, each with separate rights and transaction history. Keep the effective dates and links between parent and child records. Do not attach an earlier whole-site sale price to each later unit as though each sold for that amount. The title and subdivision documents need legal review; a portal address is not a complete ownership record.2

Keep the sale-event key separate

Record property identity, sale date, source and the evidence that two reports describe the same event. Different source publication dates do not necessarily mean separate sales. Conversely, two genuine sales of one property should remain distinct. Inspect significant discrepancies before selecting a preferred price or date. Preserve rejected duplicates and the reason they were merged for auditability.

Check shared-property arrangements

CAV discusses “Two-lot subdivisions” as a distinct topic.2 A simple-looking pair of units can still involve common property or other obligations. Address matching cannot answer access rights, liability allocation or boundaries. CAV’s due diligence checklist is a starting point for broader property-specific checks.1 Use the research key to locate documents, not to substitute for them.

Publish the counting rule

A useful report states unique premises, sale events and unresolved identity matches separately. Retain a revision record when new information joins or splits records. For a buyer, the practical output is a clean comparison sheet with document links and identity questions. That is more reliable than silently correcting addresses and presenting the result as a perfect market census.

Questions buyers ask

Should repeat sales of one address be deleted as duplicates?

No. Distinct supported sale events remain separate even when the premises is the same.

Can a parent-site price be assigned to every later subdivided unit?

No. The earlier whole-site transaction and later lot transactions are different observations.

Continue the evidence check

Use the development evidence hub to build a source-linked issue register, then compare the Development Insights methodology and current tool. These articles explain research methods; they do not reproduce proprietary transaction databases or establish an approval, valuation or future result.