the short answer
Personal trainer tax deductions are the ordinary and necessary costs of running the coaching business, which reduce taxable profit rather than revenue. 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 do not need an LLC to deduct them - you need clean records. What you do need is to keep business money separate, log costs as they happen, and have a professional in your country confirm the specifics.
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.