A Bill of Sale acts as a receipt for both parties. The seller can use it to prove that an item was sold to the purchaser "as-is", and the buyer can use it to prove that payment in full was given to the seller. It also provides a sale date to both parties, which can show when the responsibility of the item was transferred. Both the purchaser and the seller can use it as evidence of the price paid for tax purposes.
A bill of sale records important information about the exchange of personal property. It will give information about the buyer, the seller, and the property that is being sold.
This is especially true for the buyer, as it is usually the seller who has composed the bill of sale (or hired someone else to compose it). Therefore, while both the buyer and the seller must consider the terms of the sale very carefully, it is especially important for the buyer to understand the legal considerations of the bill of sale.
If the item happens to be insurable, you may need to provide documentation to prove that you are the legal owner of an item, or that you are no longer in possession of the item. A Bill of Sale, if completed correctly, can be used as proof of ownership.