It’s an interest penalty at 6% annual rate, not a flat 6%, and it’s based only on the amount short below equally paid quarterly amounts of your tax due and what you actually paid, not the total amount. I think the withholdings count equally for each quarter, so say you end up withholding $10k and paying $7.5k in Q3+Q4. Then your $25k total of 4 quarterly amounts paid might be viewed for timing purposes asThank you so much!
The federal tax penalty is prorated though right? Like if I owe 25k but paid 9k so far, I would only pay 6% interest on 16k and not the full 25k?
Q1. $2.5k from 1/4 of withholding
Q2. $2.5k from 1/4 of withholding
Q3. $10k, $2.5k from 1/4 of withholding and $7.5 estimated
Q4. $10k, $2.5k from 1/4 of withholding and $7.5 estimated
Whereas you were “supposed” to pay $6,250 for each quarter, under an equal amount approach. So ballpark Q1 is short $4k but you catch up and overpay that extra amount in Q3 (above the regular equal amount). Likewise Q2 is short $4k and gets caught up in Q4. So you’d pay 6% on $4k for 6 months, twice, which would come to about $240 plus a little more maybe in compound interest or waiting to pay the extra $240 until April or something. But this is what I mean that it’s not going to be a big number. If you really care, you can see all the details in the instructions for Form 2210.
https://www.irs.gov/forms-pubs/about-form-2210
