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Credentials
Which trades require a licence, who issues it, and what it takes to hold one. Licensing in the United States is set by states and municipalities, so this page tells you what to expect — your state board tells you what applies.
Verify with your state board before you rely on anything here
These trades gate the work itself behind a licence. Working without one is generally a misdemeanour, voids insurance coverage, and makes the work unpermittable.
Journeyman and master licenses are issued by states or municipalities; most require documented hours plus an exam.
Nearly every state licenses journeyman and master plumbers; gas fitting is often a separate endorsement.
EPA Section 608 is required nationwide to handle refrigerant. Many states add a separate HVAC contractor or mechanical license.
Generally unlicensed as a trade. A general contractor license is required in most states to contract work directly.
A CDL is usually required to move equipment. Crane operators must hold NCCCO or an equivalent certification under OSHA rules.
Many states license roofing contractors specifically; individual roofers usually are not licensed.
These trades are not licensed at the individual level in most states. That does not mean they are unregulated — the work is gated by employer qualification tests, industry certification, or the contractor licence held by whoever signs the permit.
No general license. Work is gated by weld procedure qualification tests specific to process, position and material.
What employers look for: AWS Certified Welder · ASME Section IX Procedure Qualification · AWS Certified Welding Inspector (CWI)
No general license. ASE certification is the industry standard, and EPA 609 is required for A/C work.
What employers look for: ASE A1–A8 Master Automobile Technician · ASE L1 Advanced Engine Performance · ASE L3 Light Duty Hybrid/Electric Vehicle
No license. NIMS credentials are the recognized skill standard.
What employers look for: NIMS Machining Level I–III · Mastercam / Fusion CAM Certification · ASQ Certified Quality Inspector
No general license. Employers often require specific PLC and safety credentials.
What employers look for: NCCER Industrial Maintenance · Siemens / Rockwell PLC Certification · SMRP Certified Maintenance & Reliability Technician
A short list, but an important one — these apply everywhere in the United States regardless of which state you work in.
A licence number printed on a truck or a quote proves nothing. Every state board publishes a free online lookup. Check the number, check that it is current, and check that the classification actually covers the work you are buying.
Contractor hiring checklist