What business expenses can I actually deduct?

The standard is simple to state and broad in practice: an expense is deductible if it's "ordinary and necessary" for your trade — common in your field and helpful to the business. That covers a wide range: software subscriptions, professional fees, advertising, supplies, business insurance, contractor payments, bank and merchant fees, professional development and courses, industry memberships, business travel, a portion of phone and internet, and the home office. What's not deductible: personal expenses, commuting, most clothing you could wear elsewhere, fines and penalties, political contributions, and entertainment. The test is purpose and proportion — split mixed-use costs to the business percentage. The discipline that makes this work is a dedicated business bank account and card so every business expense is captured automatically. When in doubt, ask whether you'd incur the cost if the business didn't exist.