Thank you for using justanswer. You are responsible for reporting and paying any tax due on ALL income you received during the year, whether you received the proper forms in the mail or not. The person that paid you should have and probably did file the correct forms with the IRS, and not reporting the income could be construed as fraud under the "understating of income" rules. I have included a link to the IRS website that you might find helpful.
Tax Topics - Topic 154 Forms W-2 and Form 1099-R (What to Do if Not Received)
I hope this helps you
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