Guide 01

How to read a building's sale history

Every row on a building page is a document that was filed with the City. Knowing what each kind of document is for is the difference between reading a price and misreading one.

Last reviewed 4 September 2026

A building page on this site does not show listings, asking prices or estimates. It shows documents. Each row is one instrument that somebody filed with the New York City Register, and the number in the second column is the consideration written on that instrument.

What a row actually is

Two kinds of document dominate. A deed transfers real property: a whole building, or a condominium apartment, which is real property in its own right. A Real Property Transfer Tax return is filed when a co-operative apartment changes hands, because a co-op purchase buys shares in a corporation and a proprietary lease, not real estate, so there is no deed to record. Both appear on this site and the last column always names which one you are looking at.

This matters for a practical reason. If you look for a co-op's sales among deeds you will find nothing and conclude, wrongly, that nothing has sold.

Consideration is not always price

The figure recorded is the consideration stated on the document. In an ordinary arm's length sale it is the price. In other filings it is something else: the balance of a refinancing, the value put on an interest transferred between related parties, or a figure agreed for tax purposes. This site prints it exactly as filed and never adjusts it.

Nominal and zero transfers

Transfers with no consideration at all, or a nominal one, are extremely common: an owner moving a property into a trust or a limited liability company, an estate passing to heirs, a divorce, a correction deed replacing an earlier one. Documents recording a consideration of zero are excluded from this site entirely, because a column of zeroes teaches a reader nothing and crowds out the rows that do. A very small consideration such as ten dollars against a large building is still shown; treat it as a change of legal owner rather than a market event.

One document, several lots

A single document often covers more than one tax lot: two apartments bought together, an apartment with its storage room, or a whole portfolio. Where that happens the row is marked with the number of lots the document names. The consideration on such a row is the total for everything on the document, not for the one unit you are looking at.

When a new condominium first sells, the developer conveys apartments one by one over months or years, so a building will show a dense block of transfers in its first two or three years and then far fewer. A bulk sale of many apartments at once is filed under its own property type and appears as a single very large figure. Neither pattern is a defect in the record.

Why a building can look empty

This site attaches transfers recorded from 2003 onwards. A building held by one family or one company since before then has nothing to show. A rental building that has never been sold has nothing to show. Neither is evidence of a problem.

A limit worth knowing

The most recent 40 transfers are printed in full on a building page. Where a building has more, the yearly summary above the table counts all of them, so the totals and the medians are computed over the complete record even when the list is truncated.

A short checklist

Check the instrument column before you read the number.
Check whether the row covers more than one lot.
Ignore single very small considerations against very large buildings.
Compare the yearly medians, not two individual rows.
Remember a co-op figure is the price of shares in a corporation, which carries its own share of the building's mortgage; a condominium figure is the price of real property.

Every figure quoted in this guide is computed from the same compiled data the building pages use, retrieved 2026-09-04. See methodology for the datasets and the exclusions.