Clarification--
- IF you pay a sufficiently large Estimated Tax payment for fourth quarter (due by 1/15/21), AND
- you check box C on Form 2210,
you can avoid an underpayment of estimated tax penalty.
You would need to do a trial tax return, or do the 2210 form and AI Schedule manually ( not so easy), to determine how large your estimated payment should be.
It sounds like you already know what your payment needs to be to avoid tax due on April 15th.
