As a general rule of thumb, self -
employed individuals,
sole proprietors, and anyone whose employer does not withhold tax from their paycheck need to pay estimated quarterly income taxes.
The IRS defines eligible income
as: wages, salary, tips, professional fees, bonuses, taxable alimony, commissions resulting from profits or sales, income earned if you are self -
employed and the
sole proprietor of a business, and the income you receive
as a partner for providing services.