According to Texas Department of Licensing & Regulation, air conditioning, heating and refrigeration contractors must be licensed and carry liability insurance. This includes those who perform installations, repairs or service. Technicians, who also perform work, may not have a license; however, they must work for a licensee who assumes responsibility for their work. Certification cards and certificates of registration are not the same as a license. They do not allow the contractor to perform air conditioning or refrigeration work for the public. Before you hire a contractor, make sure he or she is licensed. License numbers should appear on both sides of the contractor's vehicle, and on any proposal or invoice you receive. A license holder has passed an exam and met minimum state requirements. The license does not guarantee workmanship. 1) Do not rush into repairs or replacement equipment get a second opinion. 2) Do get at least three bids if you must replace your entire system and ask for references. 3) Watch the contractor or technician while he or she works and ask questions if actions do not seem right. 4) Do not pay the whole amount before the job is complete. Do not pay cash without a written receipt. 5) Ensure that all items agreed to are listed on any proposal or agreement.