No, you are not automatically exempt from underpayment penalty if you make quarterly payments and pay by the due date.
However, there are some exceptions to the underpayment penalty. It's likely that you met an exception and that is why you were refunded.
Some exceptions to the penalty for the 2023 tax year were:
- $0 tax liability in 2022
- You paid 90% of your 2023 tax liability
It is possible that you met one of these exceptions. To review this before filing for next time, go to: Other Tax Situations ; Underpayment penalties and choose start or edit. You need to page through this section and answer all the questions. There will be a page for the prior year tax liability that needs to be input.
If that is not the answer to your question, you can get a transcript of your tax return from the IRS that includes would show a penalty due, if they calculated one. You can do so by filing the instructions here: Transcript types for individuals and ways to order them
