Complete the application if you are engaged in business in Texas and: Sell or lease tangible personal property in Texas; or; Sell taxable services in Texas. The assumed name certificate is valid for ten years.Before you buy an existing business, find out if the business owes any Texas taxes. Browse 178 businesses for sale in Bexar County, TX on BizBuySell. All you need to do is fill out an Application to Update an Existing Certificate of Occupancy to request a name change on the existing certificate of occupancy. Bexar County provides a new form each year, but the updated form can typically be found on the Property Tax web page in the Tax Resources on the right.