Can your employer add income to your w2 you didnt earn by adding it to gross income and subtracting from net so you pay more in taxes?

Your W-2 should accurately reflect the income earned, as well as the amounts designated for FICA, Federal, State and local (if applicable) taxes, as well as any employee benefits to which you contributed. The employer cannot play accounting games with your taxes.

If you think that the payroll department made an error on your gross wages on the W-2 form box 1 then you should contact them and ask for a corrected W-2C. If you are still concerned, contact the IRS and discuss the matter directly with them.