IRS Q4 2025 interest rates: what tax pros need to know now

The IRS just announced the quarterly interest rates (which remain unchanged from Q3), effective Oct. 1, 2025. For tax professionals, these numbers aren’t just abstract percentages; they directly affect how you advise clients on late payments, refunds and corporate tax strategies.

Here are the rates for Q4 2025:

• Overpayments (individuals/non-corporate): 7%
• Corporate overpayments: 6%
• Portion of corporate overpayments exceeding $10,000: 4.5%
• Underpayments (all taxpayers): 7%
• Large corporate underpayments: 9%

These rates will appear in the Internal Revenue Bulletin 2025-37 (Sept. 8, 2025) and remain in effect through Dec. 31, 2025.

Why this matters right now

Tax season may feel far off, but interest rates impact clients today. With daily compounding under §6622, even a short delay in payment can turn into hundreds (or thousands!) of dollars in interest. For individuals, the 7% underpayment rate is high enough to make estimated tax payments a top priority. For businesses, the 9% rate on large corporate underpayments is a powerful motivator to avoid falling behind.

On the other side, clients waiting on refunds may ask whether it’s worth it to delay filing. While the 7% overpayment rate sounds attractive, corporate taxpayers get less of a benefit: just 4.5% once refunds exceed $10,000. This is where your guidance as a tax pro makes all the difference.

Example: client cash flow in focus

Suppose your corporate client overpaid $50,000 in 2024 taxes. If that refund request is delayed into Q4 2025, only the first $10,000 earns interest at 6%. The remaining $40,000 earns just 4.5%. While that still beats some bank savings accounts, the reduced rate means it’s rarely a smart cash management strategy.

Contrast that with an individual client who underpaid $25,000 in estimated taxes. Leaving the balance unpaid for 60 days racks up interest like this:

$25,000 × 7% × (60/365) ≈ $288.

That’s before penalties. Advising clients to catch up now can save them hundreds.

Action steps for practitioners

As you guide clients into year-end, here’s how to use these rates strategically:

• Review estimated payments: October is a great time to double-check whether individuals and businesses are on track.
• Educate on refund timing: Help clients weigh the benefits of leaving money with the IRS versus applying overpayments forward.
• Warn corporate clients about 9% costs: Large underpayments add up fast. Stress the importance of avoiding this costly mistake.
• Frame it as risk management: Position this update as part of your proactive compliance strategy, building trust with clients.

Big picture

These interest rates show how the IRS is keeping pace with today’s higher-rate environment. At 7% and 9%, the cost of noncompliance is steep, and that gives tax professionals an excellent opportunity to reinforce the value of timely planning and payment.

Your clients may see these rates as just numbers. But when you translate them into real-world costs and strategies, you strengthen your role as a trusted advisor.

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