Before you pick up a tool, settle whether the job is yours to do. Many local building departments set rules for work on gas lines, electrical circuits, and some heating and cooling replacements. Those rules are local, so the first answer comes from your own jurisdiction, not from a general rule of thumb.
Name the job in one plain sentence
Start with what the work actually is. Changing a filter, clearing a condensate drain, or swapping a thermostat battery usually sits outside permit territory. Replacing a whole unit, moving a gas line, or changing a panel usually does not. Write the job down as one sentence, then take that sentence to the building department and ask what it requires.
Questions to put to the department
- Does this exact job need a permit, an inspection, or both?
- May a homeowner pull the permit, or must a licensed trade pull it?
- At which stage is the inspection, and must it happen before any cover or wall goes back on?
- Does the permit tie the work to a specific model, rating, or clearance?
- What does a closed permit look like, and who keeps the copy?
What a closed permit leaves behind
A closed permit is a record that the work was reviewed. Buyers, inspectors, and insurers sometimes ask for proof of permitted work, so keep the closed record in the same folder as the equipment papers. Insurance wording differs from policy to policy, so read your own policy for what it says about unpermitted work. This is general information, not legal advice.
Compare the two paths side by side
On the owner path, you pull the permit, you do the work, you schedule the inspection, and you keep the record. On the hire-out path, a licensed trade usually pulls the permit under its own name and schedules the inspection. Ask whether you will receive a copy of the closed permit, who is named on it, and whether the quote includes removal of the old equipment, disposal, testing, and start-up. Compare those items line by line, not by the total at the bottom.
Carry the answers into the decision
Bring three things to the decision: the local rule for this exact job, the name of the person who must sign, and the inspection stages. If the rule allows owner work and the inspections are clear, the job may stay with you. If a licensed person must sign, the job moves to the hire-out column and you already know what to ask for. For planning dates on the systems involved, see the gas furnace page, which turns an install year into a planning window.