the short answer
Personal trainer tax deductions are the ordinary and necessary costs of running the coaching business, which reduce taxable profit. For online coaches that commonly means software, certifications and continuing education, equipment, a qualifying home office, the business share of phone and internet, travel, insurance, marketing and processing fees. You need clean records, not an LLC.
General information, not tax or financial advice. A coach is a coach, not a tax adviser, and tax rules vary by country and state and change every year. Treat the categories below as a starting checklist to take to a qualified accountant, not as a ruling on your specific return. No figures, percentages, or thresholds here are guarantees, and none of it promises a particular saving.