The IRS (without announcing officially) has been sending penalty letters to taxpayers who are self-employed for not paying enough in estimated taxes. I thought payment of estimated was voluntary. If you are not a W-2 employee, it appears taxpayers are now required to make estimated payments. The target dates are April 15, June 15, September 15 and January 15.
I received one of those letters even though I did pay estimated taxes for 2022. Apparently, it was not enough.
If you have any questions, I would be happy to answer those for you.