[Annual NOI] = [Yearly Rent] - [Yearly Property Mgmt] - [Insurance] - [Taxes] - [Yearly HOA Misc]

Net operating income (NOI) is simply the annual income generated by an income-producing property after taking into account all income collected from operations and deducting all expenses incurred from operations. NOI excludes any financing or tax costs incurred by the owner/investor. In other words, the NOI is unique to the property, rather than the investor.