Quarterly tax calculator for self-employed founders
Enter your quarterly revenue, business type, and state to see exactly how much to set aside — and what you owe each due date.
CaskFlow tracks your tax set-aside in real time — categorizes every transaction and updates your quarterly estimate automatically. No spreadsheet required.
Try the demo →This calculator gives you a solid estimate. CaskFlow goes further — it tracks your real revenue each month, recalculates your estimated tax exposure automatically, and reminds you before each quarterly payment is due so you never get caught short.
CaskFlow tracks your tax set-aside in real time — try the demo →No credit card. No bank connection. Takes 3 minutes.
What are quarterly estimated taxes and who has to pay them?
If you're self-employed — a sole proprietor, freelancer, 1099 contractor, or owner of a single-member LLC or S-Corp — the IRS expects you to pay taxes as you earn income, not just at the end of the year. Because nobody withholds taxes from your revenue the way an employer withholds from a W-2 paycheck, the IRS requires you to estimate your annual liability and pay it in four installments across the year.
These are called quarterly estimated tax payments, filed using IRS Form 1040-ES. Miss them or underpay, and you owe an underpayment penalty on top of the taxes you owe — currently around 8% annualized on the shortfall for each quarter.
When are quarterly estimated tax payments due?
The four deadlines are not evenly spaced — a quirk that trips up first-year founders:
- Q1 (January–March) — due April 15
- Q2 (April–May) — due June 15
- Q3 (June–August) — due September 15
- Q4 (September–December) — due January 15 of the following year
If a due date falls on a weekend or federal holiday, it shifts to the next business day. Pay via IRS Direct Pay, EFTPS (Electronic Federal Tax Payment System), or mail a check with a 1040-ES voucher.
How much should I set aside for quarterly taxes?
The right number depends on three things: your revenue, your business structure, and your state. A rough rule of thumb for a sole prop or LLC in a moderate-tax state is 28–30% of gross quarterly revenue. Here's where that comes from:
- Self-employment (SE) tax: 15.3% on net self-employment income (12.4% Social Security + 2.9% Medicare). Above $168,600 (2024 wage base), only the 2.9% Medicare piece applies. You also deduct half of SE tax from gross income, which modestly reduces income tax.
- Federal income tax: Varies with your tax bracket. The calculator uses the 2024 brackets — 10%, 12%, 22%, 24%, 32%, 35%, 37% — and assumes the standard deduction for a single filer.
- State income tax: Select your state above. Nine states have no state income tax at all; California tops out at 13.3%.
The calculator above shows your combined effective rate and breaks out what you owe per quarter based on those three inputs.
How does business structure change the number?
Sole Prop / 1099: Every dollar of net income is subject to SE tax. Simple to calculate, hardest to minimize. The default choice for freelancers and early-stage founders.
Single-member LLC: Taxed identically to a sole prop by default (called a "disregarded entity" by the IRS). The LLC provides liability protection, not tax savings. You still owe SE tax on all net profit unless you make an S-Corp election.
S-Corp election: You pay yourself a "reasonable salary" via payroll — that portion is subject to payroll taxes including the employer + employee halves of FICA. Any remaining profit is taken as a distribution, which avoids SE tax entirely. The result: founders earning over ~$60,000 in net profit typically save $5,000–$15,000/year in SE tax. The downside is added complexity: payroll filings, Form 1120-S, and accountant fees. Work with a CPA to determine whether the math pencils out for your revenue level.
What happens if I underpay?
The IRS charges an underpayment penalty calculated at the federal short-term interest rate plus 3 percentage points (currently around 8% annualized) on any shortfall for each quarter. The penalty accrues quarterly — if you skip Q1 and Q2 and catch up in Q3, you still owe penalties for the periods you were short.
The simplest way to avoid penalties entirely is the safe harbor rule: pay at least 100% of your prior year's total tax liability spread across four payments (110% if last year's AGI exceeded $150,000). Even if your income grew significantly, you owe no penalty as long as you covered the prior year's liability.