What can I write off the most for an online business?

Expenses such as website hosting, software subscriptions, advertising, and office supplies are generally deductible if they are ordinary (common and accepted in your trade) and necessary (helpful and appropriate for your business). However, personal expenses are not deductible, and mixed-use expenses (e.g., a home internet connection) must be prorated based on business use. For example, if you use your internet 50% for business, you can only deduct 50% of the cost. Additionally, capital expenses like equipment purchases may need to be depreciated over time unless they qualify for Section 179 expensing or bonus depreciation.