Thanks for the reply but things are still not clear for me. The instruction from TTax is to enter 110% of the 2023 tax. I made all the quarterly payments suggested by TTax. I overpaid my 2023 State amount due and credited the over-payment amount to 2024. Entering either the amount on line 20 from 2023 or 110% of that creates a penalty and interest charge for 2024. The question from TTax doesn't really make sense if your suggestion to enter the amount on line 20 from 2023 is correct. Anyone with an AGI exceeding $150,000 is going to have a tax liability. If more than that liability was paid on time, and in the amounts suggested by TTax, there should not be a penalty for underpayment. Can you explain further how paying the estimated payments on time results in underpayment?
