BUSINESS AND OCCUPATION TAXES - Washington is the only state whose sole business tax is based on 100% of sales (gross sales). Look up the following tax rates, then show how much tax business would owe under each type of tax if their gross sales for a month were $500,000. Retail B&O: Wholesale B&O: Service and Other Activities B&O (Attorneys, Accountants, Doctors, etc.): Prescription Drug Warehousing B&O: Manufacturing of Aluminum Smelters B&O: Manufacturing or Wholesaling of Solar Energy B&O