What if an employer does not send a 1099?

It is your responsibility to report income, regardless of the receipt of a 1099. In the event of an audit, there is a substantial possibility of the discovery of this income, and not only will you get to pay taxes on the amount, but you'll also be paying penalties and interest. Remember, 1099's are not required on amounts of less than $600. Report the income, deduct applicable expenses, and go along your merry way. That's the right way to go about it.