When is bill of sale void?

A bill of sale is a legal document to provide proof of purchase, so unless the sale of the item is somehow invalidated, it will not become void. In some cases, however, the bill of sale is just one step in the process of ownership, and the potential owner may need to take care of something else within a designated period of time to avoid the document being voided. It could also be voided if there is a mistake, and a new bill of sale will replace it.