As the buyer of a business, you could be liable for the unpaid taxes of the business. When you sell your business, you may need to report all or part of the sale on your excise tax return.Also, you may be required to collect retail sales tax. Download the Washington Bill of Sale form to securely document the transfer of property and ensure a smooth, legally compliant transaction. A business sale agreement is a legal document that describes and records the price and other details when a business owner sells the business. (1) Prepare business for sale including updating financial documents and list of business assets and debts in order to get the business potentially valued. You can fill out the Transfer Document and then bring it to a notary. Learn about different ways Notaries can incorporate their business to protect financial and personal assets.