As a profesional firefighter in South Carolina what can I write off on my taxes?

This may not encompass as much as you'd like and this may be more obvious than you'd like (and I am no accountant). But anything related to business that was at YOUR expense can theoretically be written off. Anything like new uniforms or equipment you buy WITHOUT compensation from your department will work. Miles of gas used for commuting is not applicable, but if you are not compensated for driving somewhere further for training or to do something work related then it is worth asking a licensed accountant the validity of including those.

I felt comfortable in answering this as my man is also professional firefighter and we go through this yearly :]

Stay safe!

Haircuts, since they are mandatory. Under shirts if they are mandatory. Cell phone if you use your cell phone for business use... Any Mileage, gas, tolls, or hotels for training unless they are covered. Gym memberships too.