Definition
De estimato (also spelled de aestimato) is a Roman law contract classified among the innominate contracts — that is, agreements recognized and enforceable by Roman law but not falling within one of the four named contract categories (sale, hire, loan, mandate). In de estimato, an owner of property, typically goods or land, delivered that property to a third party at an agreed appraised value (the aestimatio). The third party undertook to either sell the property to a buyer and remit the appraised price to the owner, or return the property itself if no sale was achieved. If the third party sold the goods for more than the appraised value, the surplus belonged to the third party as compensation for the arrangement.
In modern commercial terms, the structure most closely resembles a consignment arrangement: the original owner sets a floor price, a middleman finds a buyer, and any upside above the floor belongs to the middleman.
Common Language
This term has no meaningful counterpart in ordinary modern English. De estimato is Latin legal terminology without a common-use form. The word estimato relates to estimation or appraisal, but the legal construct is not derived from everyday usage and no comparison is instructive here.
Core Elements
The operative structure of de estimato requires:
1. Delivery of property — the owner transfers possession of goods or land to the intermediary.
2. Agreed appraised value (aestimatio) — a fixed price is set at the outset, which the intermediary guarantees to the owner.
3. Alternative obligation — the intermediary must either produce the appraised price (by selling to a third buyer) or return the property intact.
4. Surplus benefit — any sale price exceeding the appraised value belongs to the intermediary, not the original owner.
These elements distinguish de estimato from a straightforward sale (no buyer is yet identified, ownership does not transfer until sale) and from a simple mandate or agency (the intermediary bears financial risk, not merely acting as agent).
Why It Matters in Research
De estimato arises almost exclusively in two research contexts: Roman law scholarship and historical comparative contract law. Researchers encountering this term in English-language legal sources are most likely reading a discussion of innominate contracts as a category — the Roman taxonomy that influenced later civil law systems and, through civilian scholarship, certain aspects of equity and commercial law in common law jurisdictions.
The primary trap for researchers is conflation with related modern arrangements. A researcher reading a 19th-century treatise on commercial law that references de estimato as a precursor concept should not assume a direct doctrinal lineage into Anglo-American common law. The common law developed consignment, agency, and sale-or-return arrangements through different paths. The civilian influence was felt more directly in Louisiana, Quebec, Scotland, and South Africa, and in the historical development of continental European commercial codes.
Note also that Black's Law Dictionary entry for de estimato appears in close physical proximity to de aetate probanda — a writ for proving the age of an heir — which is an entirely unrelated concept. Researchers using older print editions or optical-character-recognition scans of Black's should take care not to run these two entries together, as the typographic boundary between them is not always clean in reproduced texts.
For researchers tracing the history of consignment or commission sale in civil law systems, de estimato is a legitimate starting point, but the path runs through Justinian's Digest and the subsequent civilian glossators, not through common law reporters or equity courts.
Historical Dictionary Support
Black's Law Dictionary identifies de estimato as one of the innominate contracts of Roman law, describing it as effectively a sale at a guaranteed appraised price where a third party undertook to find a purchaser. This is accurate and consistent with the treatment in Roman law scholarship more broadly. The innominate contract framework — do ut des, do ut facias, facio ut des, facio ut facias — provided Roman jurists a residual category for enforceable exchanges that did not fit named forms, and de estimato is a recognized member of that group.
Black's entry is brief and functional. It does not explore the actio praescriptis verbis, the Roman procedural mechanism by which innominate contracts were enforced, nor does it address the doctrinal debate among Roman jurists over whether de estimato was more properly classified as a species of sale or as a distinct unnamed agreement. For deeper treatment, researchers need to go beyond Black's to primary Roman law sources and to civilian commentators such as Pothier, whose influence on both French and Anglo-American contract thinking was substantial.
No other English-language historical legal dictionaries in the Law Mind corpus provide a meaningfully different or richer entry for this term.
Jurisdictional Note
De estimato as a live doctrinal concept is relevant primarily to civil law jurisdictions. Researchers working in Louisiana, Quebec, or comparative private law contexts may encounter functional equivalents in those systems' treatment of consignment and commission contracts. In purely common law jurisdictions, the term appears almost exclusively in historical and academic writing rather than in operative legal doctrine.