I had a couple of those.  When the dust all settled, the affected clients actually were in federally declared disaster areas (even though they weren't even close to being affected) and got some of the penalties waived because of it.  Might or might not be your issue too.

Many times!   I give clients the option to let IRS compute the penalty and send a bill, or to let PS do it, many times IRS is less than PS.....my own return last year IRS only charged me half of what PS computed.

I generally check the option to have the IRS calculate the penalty instead of PS. Probably 90% of my clients that owe, forget that I gave them that information, so starting a few years ago I make a notation on the client copy that the IRS may bill them for ES tax penalty. 2024 was was bonus year for TN, returns were not due until 11/03/2025 and no penalty or interest due to diaster decleration.

1) Are they in a disaster area that extended the payment deadlines?

2) If they paid before April 15th, did you change the date on the 2210?  It defaults to April 15th, so if your client paid before then, you would need to change it.

3) Did they pay their quarterly estimates before the due date and you didn't enter the date paid?

I just had 2 clients get small refunds. One lives in FL and they did have a disaster postponed due date.

The other doesn't live in FL but used a FL address on the return (that of the first client, her son and POA).

Both returns filed on or around October 15. I failed to take into account the disaster for the 1st one.

The second one got $150. I'm not worried about it.