Plan for Q3: Estimated Business Taxes Due by September 15th

Every quarter, business owners are reminded that taxes don’t just happen once a year in April. Estimated payments play a pretty big role in keeping a business compliant and financially stable. With the deadline for the Q3 estimated tax payment 2025 approaching on September 15th, now is the time to review your finances, calculate what you owe, and avoid costly penalties. Whether you run a sole proprietorship, partnership, LLC, or corporation, understanding and planning for quarterly estimated taxes is essential to smooth operations.

Why are Estimated Quarterlies So Important?

Unlike employees who have federal taxes withheld automatically from their paychecks, business owners and self-employed professionals must handle these obligations on their own. Estimated taxes cover income tax, self-employment tax, and, in some cases, alternative minimum tax.

If you anticipate owing at least $1,000 in federal income tax after subtracting withholding and refundable credits, the IRS generally requires you to make quarterly estimated payments. Corporations typically follow a similar rule if they expect to owe $500 or more.

Failing to pay on time can result in:

IRS penalties and interest charges that add up quickly
Unexpected year-end tax burdens that strain cash flow
Stressful audits or compliance issues if payments are missed repeatedly

Staying current on estimated taxes prevents financial disruption and demonstrates strong financial stewardship.

Key Dates for 2025 Estimated Tax Payments

The IRS sets quarterly deadlines for estimated payments each year. For 2025, the schedule is:

Q1: April 15, 2025
Q2: June 16, 2025
Q3: September 15, 2025
Q4: January 15, 2026

Occasionally, there are one or two days of grace when the 15th falls on a weekend or holiday. Although the IRS technically refers to these as quarterly payments, the months covered are not evenly divided. For example, the Q2 deadline in June comes just two months after April’s payment, while the gap between June and September is three months. This irregularity often trips up new business owners, making careful planning especially important.

Calculating Your Q3 Estimated Payment

The Q3 installment covers income earned during June, July, and August, though the IRS bases calculations on year-to-date performance. Here are the most common approaches to estimating what you owe:

Safe Harbor Rule: If you pay at least 90% of the tax you will owe for the current year, or 100% of the tax you owed in the prior year (110% if your adjusted gross income exceeded $150,000), you can avoid penalties.

Annualized Income Method: Businesses with uneven revenue throughout the year may prefer this method. It calculates payments based on actual income earned during each quarter, which can reduce overpayment during slower seasons.
Regular Installments: Some businesses simply divide last year’s total tax by four and pay equal amounts each quarter. While straightforward, this method may not align with current income levels.

Working with a CPA is the best way to ensure you choose the right method and stay compliant while minimizing overpayment.

Common Mistakes to Avoid

Quarterly estimated taxes may sound simple, but errors are frequent. Some of the most common mistakes include:

Missing the September 15 deadline – Even a one-day delay can trigger penalties
Underestimating income – Leads to underpayment and IRS notices
Forgetting self-employment tax – Covers Social Security and Medicare contributions
Ignoring state requirements – California and many other states require their own estimated tax payments
Failing to account for credits or deductions – Overpaying reduces valuable working capital

Accurate bookkeeping throughout the year is key to avoiding these issues.

How to Submit Your Payment

The IRS offers several methods to make quarterly payments, and each has its benefits:

IRS Direct Pay – A free online option that withdraws directly from your bank account
Electronic Federal Tax Payment System (EFTPS) – Recommended for businesses, allowing scheduling and tracking of payments
Debit or Credit Card – Convenient, though processing fees apply
Check or Money Order – Mailed payments must include Form 1040-ES for individuals or Form 1120-W for corporations

Electronic payment is typically fastest and ensures proper documentation for your records.

Why September 15th Is Especially Important

The September 15 deadline often catches businesses off-guard. Unlike April, which coincides with annual tax filings and tends to be top of mind, September falls during the busy late-summer season.

Missing Q3 payments can be particularly damaging because:

It leaves little time to catch up before year-end
Penalties may compound quickly if Q4 is also missed
Cash flow is often tighter as businesses prepare for the holiday season or fiscal year-end planning

Treating September 15 with the same urgency as April 15 helps keep financial obligations on track.

Planning Strategies to Stay on Track

Here are practical ways businesses can prepare for Q3 estimated taxes:

Set aside funds monthly – Create a dedicated tax savings account to avoid scrambling
Review financial statements in August – Gives a clear picture of income leading up to September
Use accounting software – Many programs can calculate estimated taxes automatically
Seek professional guidance – CPAs provide accurate projections and help avoid overpayments
Plan for state obligations – California businesses must submit quarterly estimated payments to the Franchise Tax Board, which often mirror IRS deadlines

Being proactive in Q3 prevents surprises when the final installment arrives in January.

How Can a CPA Help with Estimated Tax Planning?

For many business owners, taxes are an ongoing source of stress. Working with a CPA transforms the process into a manageable routine. A professional like Katherine M Johnson, CPA, can:

Analyze year-to-date income and project liabilities accurately
Identify deductions and credits that reduce estimated payments
Handle both federal and state filing requirements
Offer strategies to improve cash flow while meeting obligations
Provide reminders and scheduling tools so deadlines are never missed

Having a trusted advisor ensures you’re not only compliant but also making the most of your financial resources.

Need Help with 2025 Q3 Estimated Tax Payments? Call Katherine M Johnsons, CPA

The Q3 deadline is an important checkpoint for business owners. Falling behind can lead to costly penalties and cash flow headaches, while careful planning ensures your business remains on solid financial ground.

If you’re unsure how much to pay, need help projecting income, or want peace of mind knowing your taxes are accurate, Katherine M. Johnson, CPA, is here to help. With personalized guidance and professional support, you can meet the September 15 deadline confidently and keep your business finances on track. Contact us today to schedule.