Your business activity must be included on a federal tax return. Which return and when it’s due will depend on your choice of entity selection. If you are a sole proprietor or a single member LLC, put it on schedule C of your individual tax return (form 1040). Otherwise, it goes on a separate tax return. If you had expenses only but no revenue, you should still complete a return to utilize the loss either this year, or to create a net operating loss carry forward, or carry back.