Are you saying your employer gave you a W2, but that doesn't represent all that you were paid? Could be your employer treated you as a "contractor' at first and not as an employee. If that money was less than $600 than the employer does not have to give you a 1099 NEC(non employee compensation). If you think it should have been in your W2 then you should ask your employer for a corrected W2. As an employee your employer has to withhold taxes, social security, and medicare taxes (and pay 7.5% for Social Security) in addition to your part. As a 'contractor' your 'employer' doesn't have to do withholding, pay any of the SS taxes (then 15% falls on you), and they also (depends on state) may not have to pay into unemployment, and may not even carry you on their workers compensation.
I'm sure TT has a way to report income not shown on a 1099. If you got a 1099NEC you would have to add a schedule C (business) form to your return. Messy...
