What about the actual costs of running your business?

The bottom line answer is that they’re normally 100% tax deductible! The costs of starting-up your home business, promotional materials, product samples, meeting attendance, internet access fees, special phone services, fax lines, lead lists, website fees, 800-numbers, printing costs, brief cases, business cards, home office furnishings — all can be 100% deductible if they are used 100% for business.

The rule of thumb is this: any expense you incur because of your business, that you would not have incurred if you didn’t have a business, is probably deductible.