Private treaty is the British auction-trade term for a negotiated sale of jewellery, gemstones, or other property arranged outside the public auction process, with terms agreed directly between the parties through an intermediary rather than determined by competitive bidding. The term is interchangeable in practice with private sale, with which it shares essentially identical mechanics, but private treaty carries a slightly more formal and legalistic register and is the term preferred in British auction-house contracts and in the documentation of estate-sale transactions handled by the major London houses.

Etymology and use of the term

The phrase by private treaty descends from English contract law, where treaty in the older legal sense means a process of negotiation as distinct from a competitive sale or a sale under court order. A sale by private treaty is therefore one in which the price and the terms are arrived at through direct negotiation between the parties, without the determinative role of a public auction or a court-conducted process. The term has been in continuous use in English property and chattels law since the eighteenth century and is preserved in modern British auction-house terminology for off-calendar transactions.

American auction houses generally use the term private sale rather than private treaty, even where the underlying transaction structure is identical. The choice between the two terms is regional rather than substantive, and a contract that calls itself a private treaty in London would be called a private sale in New York without any change in mechanics or fee structure.

How a private treaty sale works

A private treaty sale begins when a consignor instructs an auction house, dealer, or broker to find a buyer for a specific piece, or when a buyer instructs the same kind of intermediary to find a specific piece. The intermediary develops a price expectation, contacts qualified counterparties from a private database, and conducts negotiation between the parties without putting the piece into the public auction calendar. The fee structure typically charges a single commission to the seller, ranging from a few per cent on very high-value transactions to fifteen or twenty per cent on smaller pieces, with no buyer's premium added on top.

The intermediary acts as agent for one or both sides depending on the specific arrangement. Disclosure of dual agency is required by professional ethics in most jurisdictions, and the better intermediaries are explicit about their role at the outset of the transaction. The buyer and seller may or may not meet directly; in many private treaty transactions they do not, with the intermediary handling all of the communication and viewing logistics.

Why the channel exists

Private treaty exists because not every transaction is best conducted in a public auction room. The reasons echo those for private sale generally: discretion, timing flexibility, no public failure record, and the ability to negotiate terms that an auction format does not permit. For the British market specifically, private treaty is the preferred channel for many estate sales, particularly where the executor wishes to liquidate jewellery quietly rather than expose family pieces to the public catalogue and viewing day.

Private treaty is also the preferred channel for transactions involving complex contingencies. A buyer who wants the sale conditional on independent gemmological testing, on resolution of provenance questions, on currency-exchange terms, on payment in instalments, or on any other non-standard arrangement cannot easily structure those contingencies through an auction format. Private treaty allows the parties to negotiate any contingency they can agree on and to record it in the sale documents.

Documentation and warranties

A private treaty sale is documented by a written agreement between the seller, the buyer, and the intermediary, setting out the description of the piece, the price, the terms of payment, the warranties on authenticity and condition, and any conditions or contingencies that apply. The documentation is more elaborate than the standard auction confirmation slip and typically incorporates the laboratory reports, provenance documentation, and condition reports that the parties have relied on in agreeing the sale.

Authenticity and treatment warranties are standard in private treaty documentation for fine pieces. The intermediary, often the auction house, warrants the basics in writing: species and variety identification, treatment status to the extent disclosed in the laboratory report, and provenance to the extent supportable from the documentary record. The warranties typically run for a defined period (commonly five years) and entitle the buyer to rescind the sale if the warranted facts prove materially incorrect.

Tax treatment and probate sales

Private treaty has particular importance in British estate practice. When jewellery is sold from an estate, the executor often instructs the auction house to handle the sale on the estate's behalf, and the choice between public auction and private treaty depends on the specific circumstances. Private treaty is generally preferred where the estate wishes to liquidate quickly, where the family wishes to keep the sale out of public view, or where a single qualified buyer can be identified for the most valuable pieces.

The probate value of jewellery is established at date of death by an independent valuation, and the eventual private treaty sale price feeds into the inheritance tax calculation only in limited circumstances (typically where the sale price exceeds the probate value by a margin that triggers loss-on-sale claim provisions). The mechanics of the tax treatment differ between jurisdictions and require qualified tax advice in each case.

Comparison with public auction

The choice between private treaty and public auction for a given piece depends on the seller's priorities and on the piece itself. Public auction produces transparent price discovery and is the right choice where the seller is confident of strong demand, where the publicity is welcome rather than unwanted, and where the seller can wait for the auction calendar. Private treaty produces a confidential negotiated outcome and is the right choice where any of those conditions does not hold.

For the most valuable pieces, the auction house will often present both options to the consignor and recommend one over the other based on the firm's reading of the market. The recommendation reflects the firm's view of where the best buyer is likely to be found, what price the piece is likely to achieve through each channel, and the consignor's stated priorities on discretion, timing, and risk.

In the trade

For British dealers, executors, and serious collectors, private treaty is a routine transaction format that they expect their auction house to handle competently. The terminology is part of the working vocabulary of the London trade, and a dealer or designer working at any meaningful level in the British market is on the private treaty offer lists of the major houses both as buyer and as potential consignor. The American terminology equivalent, private sale, refers to the same business done in New York, and the two channels intersect routinely as transactions are brokered across the Atlantic.

Further reading

• GIA Gems and Gemology — gem market and trade articles
• ICA — coloured stone trade reference
• International Gem Society — auction and private sale reference