Good title is a concept in property law

Property law

Property law is the area of law that governs the various forms of ownership in real property and in personal property, within the common law legal system. In the civil law system, there is a division between movable and immovable property...

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For a valid transaction to take place, the previous owner must have an indefeasible title to the property and must transfer it to the new owner. Proof of this may be difficult, since it involves proving a negative

Proving a negative

Proving a negative or negative proof may refer to:*Evidence of absence in general, such as evidence that there is no milk in a certain bowl*Modus tollens, a logical proof*Proof of impossibility, mathematics...

: first there must not be anyone with better title than the previous owner, and second the previous owner must not have already transferred title to anyone else. Possible solutions include land registration where the state certifies the quality of titles and claims to property, or (friendly) litigation after the transaction where a court rules on the quality of the transferred title.