Your old employer should have given you a W-2 or a 1099. Businesses are required to issue a W-2 (to their employees) or 1099-MISC (if you are a contract worker who is not on their payroll). They must issue one of these to each person they paid $600 or more to in a given year. If you received more than $600 from any of your employers, then they had to report the amount you were paid to the IRS. If you did not meet the qualifications for receiving either of these forms, then you must go by your own records of payments received.