People who trade cryptocurrency had a surprise in 2019.
Some cryptocurrency companies sent out (incorrectly in my view) 1099-K forms for cryptocurrency transactions. This led to the IRS looking for Schedule C income for taxpayers and assessing taxes for unreported income.

Some have said will start issuing 1099-MISC in 2020 which likewise may be incorrect. A 1099-MISC is not meant for:
At least $10 in royalties or broker payments in lieu of dividends or tax-exempt interest.
At least $600 in:
Rents.
Prizes and awards.
Other income payments.
Medical and health care payments.
Crop insurance proceeds.
Cash payments for fish (or other aquatic life) you purchase from anyone engaged in the trade or business of catching fish.
Generally, the cash paid from a notional principal contract to an individual, partnership, or estate.
Payments to an attorney.
Any fishing boat proceeds.
In addition, use Form 1099-MISC to report that you made direct sales of at least $5,000 of consumer products to a buyer for resale anywhere other than a permanent retail establishment.

If you received a 1099-K in 2019 and didn’t report that income on your return what should you do. Amend your return with a schedule C showing the income and then backing out 100% of the income with a negative number (stating that the 1099 was issued erroneously). If you had trading profits or losses, you (and didn’t report them) you should amend schedule D to reflect those using the 1099-K number as gross proceeds.

If you receive a 1099-MISC in 2020, again, you may have to file a schedule C back out the number and then report the transactions on Schedule D.

In some respects, Cryptocurrency companies are stuck in the middle. Some people accept cryptocurrency in their businesses for payment, others trade the currency and these companies can not differentiate who is who.

The main lesson is don’t ignore the form, and be sure to include that income clearly on your return where the IRS will be looking which will be Schedule C.