i filed my taxes too soon!?

You will need to file form 1040X to amend the 1040 that you filed.

  You will report the eBay income on Schedule C. The 1099 may have come with more specific instructions. Note that you owe tax on your profit (e.g if you spent $15000 on materials and ebay fees for the things you sold for $20000, then you owe tax on $5000).

You need to file an amendment and pay what you owe.

You don't make any sense.

A 1099 is simply informational.  This information should not change your taxes, since it's informational and you knew you were doing this.  So you included the money the first time you filed your taxes, right????????????????

If you didn't think you needed to pay taxes on $20K, that you earned through ebay, that is pretty short sighted. 

Melissa, WHAT were you selling on eBay?

And how the heck did you forget you were selling?   Since you already filed for 2020, you will need to file a 1040X with the appropriate forms attached.

The current version of the form comes into play at $20,000 and 200 transactions, so you must have been doing some serious selling.  The next version of the form will impact almost everybody because it will come into play at $600 for even just 1 transaction.  

For me, I occasionally sell personal-use items on eBay just to get some cash back. I keep track of what I sold, item by item and separate out the items sold at a loss.  These losses are not deductible and if reported on a form to the IRS just so the amount is accounted for, I just enter them on form 8949 with a description (personal items sold at a loss) with the same amount for proceeds and costs so it comes out to $0.For personal-use items I sold at a gain, the gain *is* taxable (whether I got a form or not).  If under a few $100s, I've done the same as the losses, just putting one total on the form.    The IRS has not complained when I've done this, but I was definitely below the 1099 cutoff. If there is a bigger gain, I'd separate by item.  If you were buying items specifically for resale, then you'd use a schedule C and have to account for "inventory" as well as expenses by category (ebay fees, paypal fees, shipping costs).  Your total sales are from that 1099.  And yes, you NEED proof that you spent the money for both expenses and for purchases.  If you were buying stuff at garage sales, a spiral notebook log would have been fine.  You don't send the proof in, but the IRS can ask to see it.

You need to amend your return.  You will owe back the refund plus any additional taxes you owe.  

You recalculate your taxes, pay the difference immediately, and then file an amended return.  Of course, you knew a month ago you made money on ebay and should have included it on your tax return then.  Also, you don't say how much of that amount was profit, so we don't know how big your problem is.