HVAC contractors are licensed to install and modify heating, ventilation and air-conditioning systems in residential and commercial buildings. HVAC contractors become subcontractors when they are hired by a primary contractor (general contractor) to complete a portion of a building project. Subcontractors must be licensed as a contractor according to state regulations. Because each state manages its own licensing process, there is no single way to become a licensed HVAC subcontractor. However, there are some similarities between each state's process that are helpful to know.

Contact your state's contractor licensing board and find out the regulations for licensing subcontractors. States will have varied regulations about the point at which a subcontractor needs to be licensed. States usually distinguish the need for licensing by the dollar amount the contractor is working for.

For instance, Tennessee requires an HVAC subcontractor to be a licensed contractor when he is working on a bid of $25,000 or more.

Identify the classification you fall into. HVAC contractors are typically listed under the “mechanical” classification. There may be several classifications to choose from within the HVAC trade.

Locate a qualifying agent who will be responsible for taking the examination portion of the license application. Qualifying agents are the people with the training and work experience in the HVAC trade. The owner of the contracting business does not have to be the qualifying agent, and the qualifying agent does not own the contractor license.

For instance, in New Mexico qualifying agents apply for a separate certification before being named as an agent in a contractor's license application. Tennessee does not require a separate license for the qualifying agent but does require a Power of Attorney to be signed by the contracting business that identifies the qualifying agent by name.

Verify your company name with the state. Assumed or fictitious business names must be unique and may need to be registered with the state before you can use them.

Register your HVAC contracting business with the state. Contractors run businesses and may be subject to state business taxes. Your state business identification number may be required on your HVAC license application.

Provide proof of financial responsibility or other financial documents. Some states require all contractors to provide proof of a bond in a designated amount. New Mexico requires a $10,000 bond. Tennessee does not require a bond for licensing but points out a bond may be necessary when you're bidding on a project. Tennessee requires applicants to provide a financial statement prepared by a CPA.

Complete and return the application and fees. Many states use a single application for all contractors and request the contractor to choose his trade from the list of contractor classifications on the application. Fees vary greatly and can be anywhere from $30 to $300 or more.

Take the required trade exam. The qualifying agent is the person authorized to complete the exam for the HVAC classification you are applying for. Most states use a third-party exam service to manage the exam-taking process. State licensing agencies typically contact the qualifying agent by mail with instructions for scheduling and taking the exam.