I teach SCUBA classes for fun on the side for minimal cost to students. It is not something that contributes to my income. To teach classes though I am required to maintain a professional membership and liability insurance. Can I deduct these as a hobby expense? What about gear maintenance and fees for access to teaching facilities?
No.
Since this is more of a hobby that a means for making a profit, these costs cannot be deducted as a business expense.
You would need to report the income on your income tax return but as miscellaneous itemized deductions are no longer allowed, you will not be able to get any sort of deduction for your expenses.
Any income received would be reported on the Federal return under "Less Common Income" as "Miscellaneous income".
If you are engaged in scuba instruction as an “ongoing trade or business”, with the intent of making a profit, then you report your income and expenses on schedule C.
The deduction for expenses related to a hobby was eliminated as part of the tax cuts and jobs act of 2018.