The definition of a deduction in business tax scenarios is anything that is considered ordinary, necessary and reasonable. It must help you to earn your business income. It must also be helpful and appropriate for your business. When considering items for your business, then, consider whether they are helpful in drawing a profit for your business. Your computer in your home office likely is whereas that same computer in your childs bedroom is not.

There are some things that are prohibited by law from being considered a deduction. This includes brides, traffic tickets, your clothing even if it is considered for business attire (uniforms are a different case), and your homes telephone line.

The item should be used solely for your business benefit. Sharing that same computer in your home office with your child still does not make it a business expense.