Not surprisingly, this meant that I wound up paying late. Uh oh. That means penalties, right? Yes, possibly. But even if it does, it’s not a big deal.
In fact, I’ve had this happen a few times in the past and, more often than not, the IRS never even notices. If they do, they’ll eventually send you a bill. But if get your payment in relatively close to the deadline, you may never hear from them.
Here’s the scoop from the excellent tax website Fairmark.com:
If you don’t pay enough estimated tax, or don’t pay on time, you’ll have to pay a penalty. It’s best to avoid this penalty, of course — but you don’t have to lose sleep over it. The penalty is equivalent to nondeductible interest on the amount you underpaid, for the period of the underpayment. If you underpay only a small amount, or you correct the underpayment quickly, the penalty will be small.
So if you’re a few days late, the most you’ll owe is a few days worth of interest — and only on the amount that was late, not your entire tax bill. And this depends on whether or not you wind up triggering a penalty at all.
Recall that penalties are due if you wind up underpaying your total tax bill by less than $1k, have paid in at least 90% of what is due for the current year, or have paid in at least 100% of what was due the preceding year.
Assuming that your late payment triggers a penalty, it can be a pain to figure out how much you owe. This calculation is done on IRS Form 2210. Or, you can do what I do. Just ignore the possibility.
If you wind up owing a penalty, the IRS will figure it out for you and, as noted above, send you a bill. This will happen after you file your return, and you can simply pay the pre-calculated penalty at that point.