If you’re self-employed, an S-corp shareholder, or anyone who doesn’t have enough withheld from a paycheck to cover what you’ll owe, you already know April 15 isn’t just the individual filing deadline. It’s also the due date for your first quarterly estimated tax payment of the year. Two deadlines landing on the same date confuses a lot of owners into treating estimated payments as a footnote to the “real” tax deadline, instead of the separate, recurring obligation they actually are.
That confusion has a cost. Estimated payments aren’t optional if you owe them, and calculating one honestly requires knowing where your business actually stands right now — not where it stood three months ago, and not a guess you’ll square up when you file next spring.
Estimated Payments Are Due Four Times a Year, Not Once
The federal schedule is fixed: April 15, June 15, September 15, and January 15 of the following year. Four payments, spaced roughly a quarter apart (the gaps aren’t perfectly even — that’s just how the calendar falls), each one meant to cover your tax liability on the income you earned in the period leading up to it.
That structure only works if you know what you earned in each period. A payment due in June has to be based on something — and “something” needs to come from your actual books, not a rough sense of how business has felt lately.
Why “I’ll True It Up at Tax Time” Doesn’t Work Here
A lot of owners carry over a habit from W-2 life: if withholding comes up short, you just settle the difference when you file. Estimated taxes don’t forgive that the same way.
The IRS expects you to pay as you earn, not just by the time you file. If your payments through the year are too low relative to what you actually owed in each period, you can end up owing an underpayment penalty — even if the total amount you eventually pay by the following April is exactly right. Paying the correct annual total late, in one lump sum, isn’t a substitute for paying something close to correct on each of the four dates. The penalty is about timing, not just the final number.
Specifically, you’re safe from that penalty if your payments through the year add up to at least 90% of what you actually owe this year, or 100% of what you owed last year — 110% if your prior-year adjusted gross income was over $150,000 ($75,000 if you file separately from a spouse). Miss that mark and the IRS currently charges 7% annual interest, compounded daily, on the shortfall for each period it went underpaid. That rate resets every quarter, so it’s worth confirming it’s still current before you rely on it.
This is also why a P&L that’s stale doesn’t help you here the way it might for other decisions. You can run a business for a quarter on instinct and still make reasonable calls. You can’t calculate a sane estimated payment from numbers that are three months out of date — you’re not estimating at that point, you’re guessing, and guessing wrong in either direction has a real cost: overpay and you’ve tied up cash you didn’t need to; underpay meaningfully and you’re looking at that penalty on top of the tax itself.
What “Current” Actually Means Here
Current doesn’t mean perfect down to the penny. It means that a week or two before each due date, you (or whoever prepares your estimate) can look at your books and trust that revenue and expenses through that point are actually recorded — not sitting three months back in an “I’ll get to it” pile.
That’s a meaningfully different bar than what a lot of owners run day to day. Books that are “good enough” for a once-a-year tax filing — cleaned up in a rush every March — are not good enough to calculate four payments spread across the year, because by definition they’re not current at three of those four moments.
The Cadence That Supports This
You don’t need a different bookkeeping system to hit this bar. You need the same foundation on a schedule that actually lines up with the payment dates. I’ve written separately about the habits that keep books clean after a cleanup — weekly categorization and monthly reconciliation — and that foundation is exactly what makes quarterly estimates possible. The difference here is just making sure your books are current in the weeks before each of the four due dates, not only once a year:
- Reconcile every month, without exception. This is the habit that makes everything else possible. If you’re reconciling monthly already, you’re never more than a few weeks from a trustworthy number, and estimating a quarterly payment becomes a matter of looking at what you’ve already recorded instead of reconstructing it under deadline pressure.
- Build in a short check-in before each due date. A week or two ahead of April 15, June 15, September 15, and January 15, take a real look at year-to-date profit and any large swings from what you expected. This is a smaller version of the monthly P&L habit, timed to the payments that actually depend on it.
- Treat a stale “uncategorized” bucket as a red flag heading into a due date, not just a general cleanliness issue. Uncategorized transactions distort the number you’re basing a payment on, and they’re worth clearing out specifically before you estimate, even if you’d normally let them sit until the monthly review.
None of this requires new software or a bigger process. It requires the same monthly rhythm, held to a slightly tighter standard four times a year instead of once.
If You’re Not Sure Where You Stand Right Now
If it’s close to a due date and you genuinely don’t know whether your books are current enough to trust an estimate, that’s worth finding out before you guess at a number. The free books health check is a fast way to see where your reconciliation status actually stands.
And if you know your books can’t support this cadence on their own — if reconciliation has been slipping, or you’re not confident translating what’s in QuickBooks into a number you’d stand behind — coaching is built for exactly this. It’s not an ongoing arrangement; it’s built to get you running the routine yourself, including the quarterly check-ins that keep an estimated payment from being a guess.
The Bottom Line
Quarterly estimated taxes turn “keep your books reasonably current” from a nice habit into a requirement with a real cost for skipping it. Four due dates a year — April 15, June 15, September 15, and January 15 — each need books that reflect where the business actually stands at that moment, not where it stood at the last year-end cleanup. The monthly reconciliation habit is the foundation; the quarterly cadence is just holding yourself to it on the schedule the payments actually demand.
Not sure your books are current enough to trust your next estimated payment? Book a free call and we’ll take a look together.