Any “ordinary and necessary” expense related to operating your business can be considered an expense, although exceptions may apply.
Basically, any expense that you pay to run, maintain, or grow your business can apply. This definitely includes the cost of inventory items and wages paid to other contractors. It also includes any bills or services used by the business as well as any equipment.
Suppose a “capital expense” (i.e., business equipment) involves an item that has a shared personal use. In that case, the filer can only deduct the portion of the item used for business. For example, if someone buys a smartphone but uses it 50% for personal use, they can only deduct 50% of the phone’s cost and 50% of the cost of cell service and data usage.
Commonly missed deductions include interest paid on business loans, marketing, and advertising costs, the costs of maintaining or improving the property, website hosting fees, consumable items used for a business like batteries, computer and office equipment, insurance, retirement plans, rental costs for business equipment, and taxes applied directly to the business (not including income tax or self-employment taxes).