A van with a phone number on the side and a business card is not a license. On Long Island the license is a county record, and anyone can look it up for free. It takes a few minutes, and it gives you somewhere to turn if the job goes wrong. A licensed contractor is someone the county can act against, and in Suffolk, the Office of Consumer Affairs says it investigates every complaint against licensed and unlicensed contractors alike.
The Nassau County rules
Nassau’s Department of Consumer Affairs licenses home improvement contractors under the county Administrative Code. Its definition of home improvement names central heating and air conditioning systems outright, alongside windows, driveways and the rest. That means a company installing or replacing a furnace, boiler or central air in a Nassau home needs a Nassau home improvement license.
Nassau says every licensed home improvement contractor must be fingerprinted.
Plumbing is separate. Nassau leaves plumbers and electricians to its towns, cities and villages, per the county’s Consumer Affairs department. For gas piping or a new water connection, the plumber’s license comes from the municipality where the work is done.
How to look one up: use Nassau’s online search for home improvement contractors and other licenses, linked in the sources below and on every contractor card on this site.
The Suffolk County rules
Suffolk’s Office of Consumer Affairs licenses home improvement contractors under Chapter 563 of the county code. Suffolk’s definition of home improvement specifically includes ductwork for heating, ventilation and air conditioning systems. It leaves out work in the electrical and plumbing fields, which Suffolk licenses separately through its own licensing boards.
That separate licensing is where HVAC gets specific in Suffolk:
- Restricted plumber, HVAC. A Suffolk restricted plumber’s license or certificate of competency for HVAC covers installing, repairing and maintaining steam, water and fluid piping on HVAC systems, indirect waste pipes, humidifiers, and tankless domestic water heating coils on oil burning equipment.
- Licensed master plumber. Suffolk’s rules reserve direct connections to the water supply, waste and drainage systems and to any gas service for a licensed master plumber.
- Restricted electrician. Suffolk issues restricted electrical licenses in categories that include HVAC and refrigeration systems and oil and gas burning equipment, per its code of rules for restricted electricians.
Suffolk’s home improvement fact sheet is blunt: it is against the law to operate a home improvement business in Suffolk County without a license. Call Consumer Affairs at (631) 853-4600 to confirm a license and check the company’s complaint history, or use the online search for contractors with valid licenses.
Matching the job to the license
| Job | Nassau | Suffolk |
|---|---|---|
| Replace a furnace, boiler or central air system | Home improvement license (covers central heating and air conditioning) | Home improvement license for the HVAC work and ductwork; piping and wiring under Suffolk’s plumbing and electrical licenses |
| Ductwork | Home improvement license | Home improvement license (ductwork for HVAC is named in the definition) |
| Gas line or new water connection | Plumber licensed by the town, city or village | Licensed master plumber |
| Boiler piping, tankless coil | Ask which town, city or village license applies | HVAC restricted plumber, or a master plumber |
| Oil burner and HVAC wiring | Ask which town, city or village license applies | Restricted electrician (oil and gas burning equipment, or HVAC) |
Sources for the table: Nassau Consumer Affairs and Suffolk County’s licensing law and codes of rules, listed below. If your job crosses lines, ask the company which license holder is doing each part.
Refrigerant certification for AC and heat pump work
Air conditioning and heat pump repairs add a federal layer. The EPA tells homeowners to use technicians who are EPA certified to handle refrigerants, which the trade calls Section 608 certification. It is a card the technician carries. Ask to see it before anyone opens the refrigerant lines.
For heat pumps there is one more list to check. PSEG Long Island only pays its rebate when the installer is one of its participating contractors, so ask for that status in writing.
Protections that come with the contract
New York’s Attorney General lays out what a home improvement contract must do, for work costing more than $500:
- be in writing, legible and in plain English, and handed to you before work begins
- list the contractor’s name, address and phone number, the approximate start and finish dates, the work and materials including brands and model numbers, and the price
- let you cancel until midnight of the third business day after signing, in writing
- put any payment taken before the job is substantially done into an escrow account at a bank in New York State, unless the contractor posts a bond instead, and tell you where that money is
Red flags from the same fact sheet: a contractor who wants the full price up front, pushes extra work you did not ask for, or will not show proof of insurance or say how your deposit is protected. Suffolk Consumer Affairs adds one more habit worth keeping: get three written estimates before you hire.
The license line on our contractor cards
Every contractor card on this site has a license line. When it shows a number with a green lamp, we found that number on the county lookup and the card shows the date. When it shows the amber lamp and lookup links, we have not checked that company yet, and you should look it up yourself. As of October 2026, no company on this site has been checked yet.