Final Call: Everything You Need to Know Before the September 16 Tax Deadline
September is one of the most important months of the year for freelancers, contractors, and anyone earning untaxed income. The September 16 estimated tax deadline marks the third quarterly payment for the tax year—and missing it can lead to costly penalties and interest.
Whether you’ve been keeping up with your estimated payments or you’re catching up after a busy summer, now is the time to get everything in order. Here’s your last‑minute guide to staying compliant and avoiding unnecessary stress.
Who Needs to Pay on September 16?
The September estimated tax deadline applies to anyone who earns income without tax automatically withheld, including:
Freelancers and contractors
Gig workers (delivery drivers, rideshare drivers, online sellers, tutors, etc.)
Self‑employed business owners
Side‑hustlers earning extra money outside their job
Landlords with rental income
Individuals with dividends, interest, or capital gains
If you expect to owe more than $1,000 (£1,000) in taxes for the year, the IRS requires quarterly payments—even if you also have a traditional job.
What This Payment Covers
Your September 16 payment covers income earned from June 1 to August 31, 2025. It includes both:
Income tax
Self‑employment tax (your Social Security and Medicare contributions)
If you earned income during these months—or earlier if you’re catching up—this payment ensures you’re staying on track with your yearly tax liability.
How to Calculate What You Owe
You have a few ways to determine your September payment:
1. The Year‑to‑Date Method
Estimate your total income so far this year, subtract your deductible expenses, and calculate how much tax you owe using Form 1040‑ES or tax software. Divide your expected annual tax by four to find your quarterly payment.
2. The Safe Harbor Method
If estimating income is difficult, you can avoid penalties by paying:
100% of last year’s total tax bill, or
110% if your income exceeded $150,000
This method provides a safety net when income fluctuates.
3. Use a Tax Calculator
Tools like the Tax Refund Calculator can help you estimate your total tax liability and determine how much to pay before the deadline.
What If You Missed Earlier Payments?
If you skipped the April or June deadlines, now’s the time to catch up. While penalties may apply, paying sooner rather than later reduces interest charges.
Even if you can’t pay the full amount, partial payments are better than none—they lower your potential penalties.
How to Make Your Payment
The IRS offers several convenient payment options:
IRS Direct Pay – Free, simple, and ideal for online payments
EFTPS (Electronic Federal Tax Payment System) – Best for business owners
Debit/credit card payments – Fees may apply
Mailing a check with Form 1040‑ES – Slower but accepted
Online payments are fastest and offer instant confirmation.
Review Your Income and Expenses Before You Pay
Before finalising your payment, take a moment to review your financials:
Are your business expenses up to date?
Did you record mileage, subscriptions, supplies, or home office costs?
Have you included all your income sources?
Accurate bookkeeping ensures you only pay what you actually owe—and nothing more.
Don’t Wait—Make Your Payment Soon
If you’re earning untaxed income, the September deadline is one you simply can’t afford to ignore. Taking action now—calculating your income, reviewing your expenses, and submitting your payment—will keep you compliant and prevent unnecessary penalties.
Use tools like the Tax Refund Calculator to understand where you stand and make smart decisions before the deadline arrives. A little preparation today goes a long way toward smoother tax filing tomorrow.