Let's assume my known AGI for 2019 is $7500 of wages income and my income threshold for federal filing was $12000. I could have skip the filing, but let's assume I filed a federal return reporting the $7500.
One year later I found out that in 2019 I also had a $2000 taxable income from hobbyist crypto mining.
Was I required to report the $2000 income on my 2019 return, since I reported another income?
Am I required to file an amended return for the year 2019 reporting the additional income, if I want to avoid consequences?
Would the cost base of the 2019 mined crypto change depending of whether I file the amended 2019 return?
Yes, you are required to amend your return to file an correct and accurate income tax return. Your cost basis should be the same, your cost basis, whether you file a return or don't file a return and does not change.
You are required to include all income on your US return if you are a resident/citizen of the U.S. if meet the requirements to be required to file a return.
If you file a return, even if you are not required to file a return, then you must include all income on it. You cannot pick and choose what income to include.e.