Q3 Estimated Tax Payments Due September 15: What Taxpayers Need to Know

Why This Matters

The third quarterly estimated tax payment deadline is approaching on September 15. If you earn income that isn’t fully covered by withholding—such as business income, self‑employment income, rental income, investment income, or pass‑through S‑corporation income—you may need to make an estimated tax payment to avoid penalties.

With the IRS expanding its use of AI and advanced analytics to identify underpayment patterns, staying current with estimated tax payments is more important than ever. Accurate quarterly payments help reduce audit risk and keep your tax profile compliant.

This guide explains who must pay, how to calculate your payment, and what Maryland taxpayers should pay special attention to.

Who Needs to Make Estimated Tax Payments?

You may need to pay estimated taxes if you expect to owe $1,000 or more in federal tax for the year after subtracting withholding and refundable credits.

Common situations include:

• Self‑employed individuals

• Small business owners

• Independent contractors

• Freelancers

• Landlords

• Investors with capital gains or dividends

• S‑corporation shareholders (including Maryland PTE election participants)

If your withholding does not cover your tax liability, estimated payments help you avoid underpayment penalties.

How Estimated Taxes Work

The IRS uses a "pay‑as‑you‑go" system. Instead of paying all your tax in April, you pay throughout the year in four installments:

• Q1: April 15

• Q2: June 15

• Q3: September 15

• Q4: January 15 (of next year)

Missing or underpaying a quarter can trigger penalties—even if you catch up later.

How to Calculate Your Q3 Payment

Most taxpayers use one of two methods:

1. Safe Harbor Method (Most Common)

You avoid penalties if you pay:

• 100% of last year's total tax, or

• 110% if your AGI was over $150,000

Payments are divided across the four quarters.

2. Current‑Year Method

You estimate your actual 2026 income and pay tax based on what you expect to owe.

This method is more accurate but requires careful tracking of:

• Business income

• Investment gains

• Rental income

• S‑corporation distributions

• Withholding changes

If your income fluctuates, this method may reduce your quarterly payments—but it must be calculated correctly.

Maryland‑Specific Considerations

Maryland taxpayers should pay attention to:

1. Maryland Estimated Tax Requirements

Maryland follows similar rules to the IRS: you must pay if you expect to owe $500 or more in Maryland tax for the year.

2. Maryland PTE Election (S‑Corporations)

If you elected Maryland PTE (Pass‑Through Entity) tax:

• Your S‑corporation may need to make a Q3 PTE payment

• You, as the shareholder, may still need to make personal estimated payments depending on county tax and withholding

Many taxpayers mistakenly believe PTE covers everything—it does not.

How to Make Your Q3 Payment

Federal Payments

Pay through IRS Direct Pay:

• "Estimated Tax"

• "1040‑ES"

• Tax year: 2026

Maryland Payments

Pay through Maryland Tax Connect:

• "Estimated Tax"

• "Form 502D" for individuals

• "Form 510/511D" for PTE entities

What Happens If You Don't Pay?

If you miss the September 15 deadline:

• The IRS may assess underpayment penalties

• Maryland may assess state penalties

• Penalties accrue monthly until paid

• Even small underpayments can trigger penalties

With AI‑driven analytics reviewing payment patterns more efficiently, consistent quarterly compliance helps reduce unnecessary scrutiny.

Paying late is better than not paying at all.

Final Thoughts

The September 15 estimated tax deadline is one of the most important tax dates of the year for individuals and small business owners. Making your Q3 payment on time helps you:

• Avoid penalties

• Stay compliant

• Prevent a large tax bill in April

• Keep your tax profile clean as IRS enforcement modernizes

If you're unsure how much to pay—or whether you need to pay at all—consult a qualified tax professional who can review your income, withholding, and Maryland‑specific requirements.