You must provide the addendum. TREC rules require a license holder to provide the Addendum for Sale of Other Property by Buyer to a buyer who wants to make a contract contingent on the sale of another property. License holders are not allowed to write language into the Special Provisions Paragraph for situations that are covered by a TREC promulgated form, such as the contingency addendum. If your client doesn’t want to use the addendum, you should advise him to consult his attorney to draft language that will reflect his intention.
Source: TAR