I hope you have kept very good records of all of your expenses. You are most likely treated as an independent contractor by the company hiring you and will owe self-employment tax of 15.3 percent of your profit in addition to your income tax when you file your 2018 federal return. One way to know if you are treated as an independent contractor is if the company withheld social security from your pay. If they didn't, you will get a 1099-MISC in January showing everything they paid you. You must then file a Schedule C (Profit and Loss) with your income tax return to report that income and your expenses.