- Identifying Numbers
- Imputed (or Unstated) Interest
- Incentive Stock Option
- Income
- Income Averaging
- Independent Contractor
- Individual Retirement Arrangement (IRA)
- Information Returns
- Inheritance
- Insolvency
- Installment agreement
- Installment Method
- Insurance Dividends
- Intangible Personal Property
- Interest Received
- Internal Revenue Service (IRS)
- Inventory
- Investment Interest
- Investment Property
- Investment Tax Credit
- Involuntary Conversion
- Itemized Deductions