I'm in Florida and my question is for a service change, do I HAVE to pull a permit or is it an option?
The law says you absolutely are required to pull a permit for any change to a wiring system except very minor ones like changing a receptacle, GFCI, light fixture, or switch. This includes anytime you add wire such as extending an existing circuit. That said, it is rare to see an electrician actually pull a permit for very small jobs. However, a panel change is not a small job.
Congratulations, Oscar. One thing to keep in mind is just because you can "get away" with something doesn't necessarily mean you should. Now that you're the responsible party all liability falls squarely on your shoulders. Having the building department inspect your work is to have a second set of eyes checking your installation. Inspectors aren't cops, even though some act like it, they're code enforcement, making sure that your installation is code compliant and safe. Plus, having a permit and inspection adds resale value to the home, you also want to consider your customers best interests.
Also, add the approximate cost of the permit and your labor for standing the inspection to your bid.
I would add this. It's not unusual for inspectors who are driving through a neighborhood to stop when they see two of more tradesman vans at a residence to see if a permit is displayed. If you are caught doing work without a permit you will receive a penalty which ranges from paying double for the permit, to being reported to the electrical board who can fine you and pull your licence.
You can also get caught by a home inspector or insurance inspector who looks up permits in the public records and finds none where pulled. This will cause the home owner concern and they might call up the county to ask questions. Questions you don't want them asking.
Don't be afraid of the inspectors. Most are very nice and will answer questions about a job before you start it so you are sure you are doing it right. You will get red tagged a few times. This is a learning process. After a while almost all your jobs will pass first time.
It helps offset the cost of standing around and waiting for the inspector to arrive.
I personally rarely wait for inspectors. You don't have to be there, but probably will want to for the first few so you can get a feel for what the inspectors want. My contracts include language advising clients they are responsible for being present for the inspector. This lessens my costs and the price of the job. If the panel is outside and accessible (no locked gate or dogs) then nobody has to be there.