With regard to what qualifies as a business expense, you can deduct anything you spend money on that is for the pursuit of the production of income. The burden of proof is on you to maintain and to be able to provide sufficient documentation as to when, how much, to whom, where, and for what the expense was incurred. There are limitations for "lavish and extravagant" expenses for instance, so just any amount you spend is not necessarily deductible. When gathering your expenses, review your credit card charges, checks you have written, and cash receipts you have kept. If you need a list to help jog your memory, then here is a partial guideline:
Abandonment losses if business related.
Accounting and auditing expenses.
Advances to employees cancelled as bonus.
Advertising and promotion expenses.
Amortization.
Trade association dues.
Attorney's fees involving law suits in connection with your business or for the collection of income.
Attorney's fees involving business transactions.
Auto expenses.
Bad debts (if on accrual basis of accounting).
Bank charges.
Bonuses as additional compensation to employees.
Bookkeeping services.
Casualty damages (unreimbursed) from fire, rain, etc.
Charitable contributions (Sole Proprietor deducts on Schedule A, Business Tax Return has income limitation).
Cleaning.
Club expenses in connection with client entertainment.
Collection expenses.
Condemnation expenses if business property.
Contact development expenses.
Convention expenses.
Commissions.
Communication expenses.
Computers, monitors, printers (depreciate).
Continuing education.
Contract labor.
Copying.
Credit card merchant fees.
Credit reports and credit bureau fees.
Decorating and refurnishing (depreciate).
Delivery expenses.
Depletion.
Depreciation.
Dues.
Embezzlement not covered by insurance.
Engineering, zoning, plotting (depreciate).
Entertainment expenses (50% limitation).
Entertainer's cost of sheet music, agent fees, etc.
Exhibit and display expenses.
Fees to brokers and agents.
Fidelity and surety bond.
Finance charges.
Franchise fees.
Freight expenses.
Furniture and fixtures (depreciate).
Gifts to employees, business associates (Limit $25).
Goodwill, cost of, amortized over 15 years.
Guarantor's loss.
Insurance, contents and liability.
Insurance, health.
Insurance, life, if company is named beneficiary.
Insurance, workman's compensation.
Internet access fees.
Interest on proceeds from loans used for business.
Inventory loss due to damages, waste, obsolescence.
Investment counsel.
Janitorial.
Landscaping (depreciate).
Laundry and cleaning (may be subject to limitation)
Lawsuit expenses.
Lease expenses, if business related.
Leasehold improvements (depreciate).
Licenses and fees.
Living quarters furnished to employees for business.
Loans, if uncollectible, and business related.
Lobbying costs, if legal, and if connected to business.
Management fees.
Materials and supplies.
Meals for clients and customers (50% limitation).
Meals for employees (may be subject to limitation).
Messenger services.
Moving costs.
Net operating loss.
Occupation expenses.
Office expenses.
Online computer services.
Parking.
Passport fees if necessary for business travel.
Pass-through entity loss, if profit motivated venture.
Pension and retirement plan contributions.
Periodicals.
Permits and fees.
Postage.
Printing and duplication.
Professional association dues.
Pursuit costs of abandoned projects.
Relocation costs.
Rental car for business purposes.
Rent for storage of business property.
Rent for office.
Repairs and maintenance.
Research and experimental expenses.
Retirement plan.
Royalties.
Safe deposit box.
Salaries, bonuses, commissions, management fees.
Salary expense.
Sale of assets at a loss.
Sale of securities at a loss.
Self insurers, actual loss, in year of loss.
Selling expenses.
Seminars and trade shows.
Service contracts.
Small tools and equipment if useful life is less than one year or amount is immaterial.