The Short Version
Quarterly estimated taxes are one of those things no one explains when you start a construction business. You come from a W-2 job where taxes were withheld automatically. Now you're running a $700K remodeling operation, writing checks to suppliers and subs, and paying yourself — and the IRS wants four tax payments per year that nobody told you about. I've seen builders get hit with $4,000–$8,000 in underpayment penalties in a single year because they didn't know this system existed. That money is gone. Let's make sure it doesn't happen to you.
Sound Familiar?
Signs your quarterly tax system is broken or missing:
- You write one large check to the IRS in April and wonder why your accountant keeps talking about penalties
- You didn't make any quarterly payments last year and got a penalty notice — but you paid your taxes in full in April
- You're profitable on paper but your bank account doesn't reflect it, and you're not sure where the money is going
- Your bookkeeper and accountant are two different people who don't talk to each other, so no one is managing your quarterly obligations
- You had a significantly better year than last year but made the same quarterly payments — and now you're scrambling
What We Found
Why Quarterly Taxes Blindside Construction Business Owners
Quarterly estimated taxes blindside construction owners for a simple reason: the W-2 world doesn't exist anymore. When you worked for someone else, federal, state, and FICA taxes were withheld from every paycheck automatically. You never saw that money. It was gone before it hit your account.
When you run your own construction business, that doesn't happen. You invoice, collect, pay expenses, pay subs, and pay yourself — and the IRS gets nothing until you send them something. If you don't send them something four times per year, they charge you a penalty for underpayment even if you pay every dollar you owe in April.
The underpayment penalty isn't enormous — it runs around 8% annually on the underpaid amount — but it adds up. A builder who skips all four quarterly payments on a $50,000 tax liability is looking at roughly $4,000 in penalties on top of the $50,000 owed. That's money with no return. It doesn't buy you anything.
The other pattern I see: builders who know they should make quarterly payments but don't know how much to send. So they estimate conservatively, send something small, and still end up with a penalty at year-end because their conservative estimate was too conservative. Neither the "send nothing" approach nor the "send whatever feels right" approach works. You need a calculation method.
The Four Quarterly Due Dates
Federal estimated tax due dates for 2026:
- Q1 (Jan 1 – Mar 31): Due April 15
- Q2 (Apr 1 – May 31): Due June 16
- Q3 (Jun 1 – Aug 31): Due September 15
- Q4 (Sep 1 – Dec 31): Due January 15 of the following year
Note: Q2 covers only two months, not three. This is intentional — and it trips up a lot of first-time estimated tax payers who assume it's evenly split.
State estimated taxes follow a similar pattern but the due dates vary by state. California, for example, front-loads the requirement: 30% is due in Q1 and 40% in Q2, with only 0% in Q3 and 30% in Q4. If you operate in California, Texas, or any state with income tax, verify your state-specific schedule with your accountant. Federal and state due dates are often different by days or weeks.
Two Methods for Calculating What You Owe
There are two IRS-approved methods for calculating quarterly estimated taxes. One is simpler. One is more precise. The right choice depends on how predictable your income is year over year.
Method 1: The Safe Harbor Method
The safe harbor method is simple: pay 100% of last year's total tax liability in four equal installments. If your 2025 federal tax return showed $42,000 in total tax owed, send the IRS $10,500 each quarter in 2026. As long as you do that, you owe no underpayment penalty — even if your actual 2026 tax liability turns out to be $90,000 because you had a breakout year.
For high earners (adjusted gross income over $150,000 on last year's return), the safe harbor threshold bumps to 110% of last year's liability. So if last year's AGI exceeded $150K, you'd send $10,500 × 1.10 = $11,550 per quarter instead of $10,500.
This is the method I recommend to most builders in the $500K–$2M revenue range. Why: construction revenue is lumpy. You land a big job in Q3 and your income for the year looks nothing like Q2 suggested. The safe harbor method removes the guessing. You know exactly what to send each quarter. No surprises at year-end except the question of how much you overpaid.
Method 2: The 90% Method
The 90% method requires paying 90% of your actual current-year tax liability in quarterly installments. This means estimating your income every quarter, calculating your projected annual tax liability, and sending payments based on that projection.
For a builder having a significantly worse year than last year — say, revenue dropped from $1.8M to $900K due to a slow permit environment — the 90% method means smaller quarterly payments than the safe harbor method would require. That keeps more cash in your business during a lean period.
The downside: it requires more math and more communication with your bookkeeper. If your projections are wrong and you undershoot by more than 10%, you're back in penalty territory. Most builders I work with don't have the financial visibility to run this method accurately without a monthly bookkeeping relationship. If you're paying a bookkeeper quarterly or annually, stick with safe harbor.
Which Method to Use: A Quick Decision Rule
Had a relatively consistent revenue year? Use safe harbor. Growing rapidly or had a dramatically different year than last year? Discuss the 90% method with your accountant. The penalty savings from using the right method on a high-growth year can exceed $3,000–$5,000. That's a 30-minute conversation worth having.
One more consideration: if this is your first full year running a construction business with no prior year's tax return, you have no "last year's liability" to base safe harbor on. In year one, the 90% method is your only option. Get a good estimate from your accountant after Q1 closes and build from there.
The Bank Account Setup That Makes This Automatic
The practical problem isn't knowing what to pay — it's having the money available when the payment is due. Construction cash flow is notoriously uneven. A builder might collect $180,000 in draws during Q2 and $40,000 in Q3. If your tax money isn't set aside from Q2, you'll be scrambling in September to cover a $10,000 tax payment.
The system I set up with builders is straightforward. Open a dedicated tax account — a separate checking or savings account labeled "Tax Reserve" — and transfer a fixed percentage of every client payment you receive into it automatically. Don't commingle this with operating funds. Don't touch it for payroll or materials.
The percentage to reserve depends on your effective tax rate. For most construction business owners at $500K–$2M in revenue, federal income tax plus self-employment tax (for sole proprietors/partnerships) or payroll taxes (for S-corps) lands in the 25–35% range on net profit. For an S-corp owner paying themselves a reasonable salary with the rest as distributions, the blended effective rate on total business income is typically closer to 22–28%.
A simple rule that works for most builders I've onboarded: reserve 30% of every owner draw or distribution into the tax account. When quarterly payments come due, the money is sitting there. This feels conservative — and it is, intentionally. Any excess in the tax account at year-end becomes a bonus, a retained earnings boost, or Q1 of next year's payment. The alternative — scrambling to find $10,000 in September — is worse.
For builders using QuickBooks, set up a rule that automatically tags these transfers. Your bookkeeper can then reconcile the tax reserve account separately from operating accounts, and your financial reports reflect the actual cash available for business operations rather than the misleading "I have $85,000 in checking" number that includes next quarter's tax payment.
The S-Corp Wrinkle
If you've elected S-corp status for your construction business (common at $80K+ in net profit), your tax structure is different. You're on payroll for your reasonable salary — which means payroll taxes are withheld and remitted semi-weekly or monthly, not quarterly. The quarterly estimated tax payment covers income tax on S-corp distributions above your salary, plus any state-specific pass-through taxes. This distinction matters: many S-corp builders I work with think they've covered their tax obligation through payroll withholding and skip the quarterly payment on distributions. That's wrong, and the resulting penalty is avoidable.
If your net profit has grown significantly this year, don't wait until Q4 to flag it to your accountant. Call or email after Q2 closes. Give them the YTD numbers. Let them adjust your Q3 and Q4 payments. Catching a $20,000 swing in projected liability in July is fixable. Discovering it in April is expensive.
How This Fits Into Your Financial Operating System
Quarterly estimated taxes don't live in isolation. They're one output of a functioning financial operating system — monthly P&L review, job costing, cash flow projection, and bookkeeping that's current within 15 days of month-end.
The builders I see getting blindsided by tax bills are almost always the same builders who are also surprised by their actual margins on completed projects. Both problems trace back to the same root cause: no financial visibility. The money flows in and out, but no one is tracking what it means in real time.
The financial operating system I build with builders has five components: current bookkeeping (under 15 days lag), a monthly P&L meeting, a rolling 90-day cash flow projection, a tax reserve account, and a quarterly check-in with their CPA. When all five are running, estimated tax payments become routine — a scheduled transfer, not a crisis.
The Financial Clarity track of Go First's consulting work covers the full implementation: bookkeeping setup or cleanup, QuickBooks structure, payroll configuration, and the quarterly tax system. Most builders complete that track in 4–6 weeks. The tax reserve alone usually pays for the engagement within the first year.
Get Your Financial System Running Right
Most construction business owners are running their finances on guesswork. The strategy call is where we identify the gaps and build a 90-day plan to fix them.
Book a Strategy CallFrequently Asked Questions
Yes, if you expect to owe more than $1,000 in federal income taxes for the year and you don't have sufficient withholding to cover it. Most construction business owners operating as an LLC, sole proprietor, or S-corp fall into this category. The four due dates are April 15, June 16, September 15, and January 15. Missing quarterly payments results in an underpayment penalty even if you pay everything you owe by April.
The safe harbor method means paying 100% of last year's total federal tax liability in four equal quarterly installments (110% if your prior-year AGI exceeded $150,000). As long as you send these payments on time, you owe no underpayment penalty at year-end regardless of how much your actual tax liability increased. It's the simplest approach for construction business owners with reasonably stable year-over-year revenue.
For most construction business owners at $500K–$2M in revenue, reserving 25–35% of net profit covers federal and state income tax plus self-employment or payroll taxes. A practical rule: move 30% of every owner draw or distribution into a dedicated tax reserve account. Adjust this percentage annually with your accountant based on your effective tax rate, which changes as your income and business structure evolve.
You'll owe an underpayment penalty calculated at the current IRS underpayment rate (approximately 8% annually as of 2026) on the shortfall for each day it was underpaid. The penalty applies even if you pay your full tax bill on time in April — the IRS considers payments made on the April deadline to be late for the Q1–Q3 portions. Penalties typically run $2,000–$6,000 for builders who skip all four quarterly payments on a $40,000–$60,000 annual tax liability.
S-corp election changes the structure but doesn't eliminate estimated taxes entirely. As an S-corp shareholder-employee, payroll taxes are withheld from your salary and remitted on a payroll schedule. However, income tax on S-corp distributions above your salary still requires quarterly estimated payments. Many builders assume payroll withholding covers everything and skip the quarterly payment on distributions — that's an underpayment error. Confirm your full quarterly obligation with your CPA after electing S-corp status.
