Compliance
Federal Backup Withholding & Interest Rate Changes: Key Updates for Businesses and Individuals
Learn how the IRS’s threshold changes for third-party backup withholding, and the updated federal interest rates starting Q4 2026, could affect your payments and compliance practices.
By NomadicTax Research Team • 5-8 min read • August 31, 2026
## What’s Changed: Backup Withholding & Interest Rates
Two significant federal updates published by the IRS in **Internal Revenue Bulletin 2026-36 (August 31, 2026)**: (1) final regulations concerning backup withholding under **section 3406**, and (2) updated federal interest rates for overpayments and underpayments for the quarter beginning **October 1, 2026**. ([irs.gov](https://www.irs.gov/irb/2026-36_irb?utm_source=openai))
### Backup Withholding Thresholds (Section 3406)
- New rules alter when **third-party settlement organizations (TPSOs)** must perform backup withholding. Those changes stem from amendments to section 3406 by the One, Big, Beautiful Bill Act. ([irs.gov](https://www.irs.gov/irb/2026-36_irb?utm_source=openai))
- The regulations clarify the amount subject to withholding, especially in relation to “de minimis” payments under section 6050W(e). TPSOs must review payments still subject to withholding versus those exempt or limited by thresholds. ([irs.gov](https://www.irs.gov/irb/2026-36_irb?utm_source=openai))
### Interest Rates Q4 2026
- For the calendar quarter beginning **October 1, 2026**, the interest rate on underpayments is set at **7%**. Same rate applies to overpayments except for corporate overpayments (6%), and large corporate underpayments are at **9%**. For corporate overpayments exceeding $10,000, interest is **4.5%**. ([irs.gov](https://www.irs.gov/irb/2026-36_irb?utm_source=openai))
## Implications & Action Items
### For Businesses & TPSOs
- Review payment practices through TPSOs (e.g., gig platforms, payment processors): see whether payments fall under threshold exceptions or require backup withholding. If in doubt, consult section 6050W(e) de minimis payments or review how “covered payment” and “settlement organization” are defined.
- Update internal policy documentation and vendor agreements to ensure correct reporting and withholding, especially where platforms are involved in paying independent contractors, online sellers, or gig workers.
### For Individuals & Investors
- Large refunds (overpayments) will earn **lower interest** if they are corporate overpayments over $10,000, so timing of payments and use of estimated tax or withholding could matter.
- Underpayments will be penalized at **7%**, and even higher for large corporates. Adjust estimated tax payments, especially for those with large business income or investments.
## Example Scenarios
- **Freelance platform paying via a TPSO**: If your platform is a TPSO and pays you $600 but meets the de minimis exception under the new rules, backup withholding may not be required. But if payments increase, withholding thresholds apply.
- **Corporate refund situation**: A corporation expecting a large refund over $10,000 should know that its overpayment interest rate will be 6%, not the standard 7%, and about 4.5% for the portion exceeding $10,000.
## Compliance Reminder
- Clearly document when and how income came through TPSOs, keep records of thresholds met or not, and organic capacity to withhold if rules require it.
- Monitor IRS guidance or training materials—these final regulations are effective now or very soon; companies should ensure readiness for Q4 2026.
## Summary
These developments require businesses and individuals to pay careful attention: backup withholding thresholds for third-party settlement organizations have shifted, and federal interest rates for both overpayments and underpayments have also changed as of October 1, 2026. Proper documentation, updated internal policy, and proactive tax payment strategies can help minimize surprises.