An asset purchase agreement is the legal document that will govern the transfer of ownership of a business's assets from the seller to the buyer. An Asset Purchase Agreement is a legally binding contract between a buyer and a seller that details the terms and conditions of the sale of a business's assets.Parties and Recitals. An asset purchase agreement (APA) is a written legal document that formalizes purchasing a business or substantial commercial asset. An APA, or Asset Purchase Agreement, is a contract in which a buyer and seller agree to the transfer of ownership for an asset at an agreed price.