September always seems to sneak up on you, doesn’t it?
One minute, you’re enjoying summer, and the next, you realize the year is nearly three-quarters over.
For anyone who pays quarterly estimated taxes, that means one thing: your Q3 payment is due on September 15.
If you’re self-employed, running a business, freelancing, or earning income outside of a traditional paycheck, estimated taxes are a big deal.
Unlike employees who have taxes withheld automatically, you’re responsible for sending the IRS what you owe throughout the year. Missing these deadlines can lead to penalties, stress, and a nasty surprise come April.
But don’t worry—this final check-in will guide you through what you need to know about the September 15 due date. You’ll learn why this quarter matters, how to calculate your payment, mistakes to avoid, and strategies to make the process easier.
Let’s dive in so you can stay on track and avoid any last-minute scrambling.
What Are Estimated Taxes?
Estimated taxes are payments you make to the IRS throughout the year to cover income that doesn’t have automatic tax withholding.
If you only get income from a regular W-2 job, your employer handles this for you.
But if you’re self-employed, freelancing, or making money from investments, you’ll likely need to make estimated payments.
Think of it this way: the IRS wants to collect taxes as you earn income—not in one big chunk at the end of the year.
Estimated taxes keep you in compliance and prevent you from owing a huge amount on Tax Day.
Here are some examples of people who usually need to pay estimated taxes:
- Freelancers and gig workers
- Small business owners
- Independent contractors
- Investors with significant dividend or capital gains income
- Retirees with taxable distributions
If you expect to owe at least $1,000 in taxes for the year (after subtracting withholding and credits), chances are you need to make quarterly estimated payments.
Why Sept. 15 Matters: The Q3 Payment Deadline
The IRS splits the year into four tax quarters, and September 15 marks the deadline for Quarter 3.
Here’s the breakdown:
- Q1 covers January–March (payment due April 15)
- Q2 covers April–May (payment due June 15)
- Q3 covers June–August (payment due September 15)
- Q4 covers September–December (payment due January 15 of the next year)
The Q3 payment is especially important because it helps you avoid underpayment penalties before heading into the final stretch of the year.
With just one quarter left after this, you don’t have much room to “catch up” if you’ve been underpaying.
How to Calculate Your Q3 Estimated Taxes
Calculating your Q3 payment doesn’t have to feel overwhelming.
Here’s a simple step-by-step guide:
Step 1: Estimate your total annual income.
Look at how much you’ve earned so far and project what you expect for the rest of the year.
Step 2: Factor in deductions and credits.
These could include business expenses, the standard deduction, or tax credits like the child tax credit.
Step 3: Apply the correct tax rates.
For self-employed folks, don’t forget to include self-employment tax (Social Security and Medicare).
Step 4: Divide by four.
Take the total you expect to owe for the year and split it into four quarterly payments.
Let’s say you’re a freelancer who expects to earn $80,000 this year after deductions.
You estimate your tax liability to be around $16,000. Divide that by four, and your quarterly payments should be $4,000.
Of course, income isn’t always predictable. If your earnings fluctuate, you can adjust each quarter’s payment. The IRS Form 1040-ES includes a worksheet to help you run the numbers, and there are plenty of online calculators to simplify the process.
Tip: It’s usually safer to overestimate a little than to underpay. Overpayments roll forward or get refunded at tax time.
Common Mistakes to Avoid
Paying estimated taxes seems straightforward, but plenty of people run into trouble.
Here are some common pitfalls to watch out for:
Forgetting income sources: Maybe you remembered your freelance gigs but forgot about investment dividends or rental income. The IRS doesn’t forget.
Relying only on last year’s income: Your financial situation might have changed. If you earned more this year, using last year’s numbers can leave you short.
Missing deadlines: Even if you eventually pay, the IRS can tack on penalties and interest if your payment is late.
Ignoring self-employment tax: Many first-time freelancers underestimate what they owe because they don’t factor in this extra 15.3% tax.
Not adjusting for life changes: Marriage, having a baby, or starting a new job can all affect your tax liability.
Avoiding these mistakes helps you stay in control and saves you from unnecessary headaches.
