Latin for “vacant goods”, used to refer to ownerless property, which by law passes to the Crown. It mainly refers to unclaimed estates (ie the property of deceased persons, where it is not clear to whom it should pass, if anyone) or the assets of dissolved companies.
The Bona Vacantia Division (BVD) is a subdivision of the Government legal department.
Where no one else has been appointed to do so, the Treasury Solicitor acts for the Crown to administer the estates of people who die intestate (without a Will) and without known kin (entitled blood relatives) and collect the assets of dissolved companies and other various ownerless goods in England and Wales.
By way of a corporate example (highlighted in bold): Leon v Attorney General  EWHC 3026 (Ch);  Bus LR 618 per Arnold J:
“ The consequence of Frinton Ltd’s dissolution was that ‘all property and rights whatsoever vested in or held on trust for the company immediately before its dissolution (including leasehold property, but not including property held by the company on trust for another person)’ were deemed to be bona vacantia, and hence to belong to the Crown, pursuant to section 1012 of the Companies Act 2006.”
By way of another example, relating to unclaimed estates (ditto): Ilott v Mitson (No 2) (sub nom Ilott v The Blue Cross)  UKSC 17;  AC 545 per Lord Hughes JSC:
 Oliver J’s reference to necessitous circumstances not by themselves always being sufficient is illustrated by Cameron v Treasury Solicitor  2 FLR 716. The claimant was the former wife of the deceased. She had been divorced from him 19 years before his death and their matrimonial finances had been settled by a lump sum paid to her as a clean break. There had been no financial relationship between them for the next 19 years, although they had remained in touch. The fact that she was in necessitous circumstances was held not to create any obligation on him to provide for her from his estate; that there was no other claimant and his small estate passed as bona vacantia to the Crown did not alter the fact that their personal and financial relationship was long in the past. Thus cases of long estrangement may, according to the judge’s assessment of the particular facts, be an example of the proposition that needs are not always enough to justify a claim under the Act. In most cases of clean break matrimonial settlement, the family court order will these days incorporate, as often as not by consent, a direction under section 15 that neither spouse shall be entitled to make any claim under the Inheritance (Provision for Family and Dependants) Act 1975 from the estate of the other.”