When you must pay estimated tax and file your tax return depends on whether you receive at least two-thirds of your total gross income from fishing in the current or prior year.
Gross income is discussed later.
Your 1999 tax return must cover all 12 months. Gross income is all income you receive in the form of money, goods, property, and services that is not exempt from tax. Gross income is not the same as total income shown on line 22 of Form 1040. On a joint return, you must add your spouse's gross income to your gross income. Wages, salaries, tips, etc.