The IRS underpayment and overpayment interest rate rose to 7% for the quarter beginning July 1, 2026, up from 6% in Q2 2026, and applies to both individuals and corporations. The rate, which compounds daily, also governs estimated-tax underpayment penalties for the quarter and stays in effect through September 30, 2026.
Home › Founders News › Taxes & Grants
IRS interest rate climbs to 7% for Q3 2026 underpayments and refunds
Why this matters for founders
Underpaying quarterly estimated taxes now costs 7% annualized, so recompute your Q3 estimate (due Sept 15) and top up withholding to hit a safe-harbor payment and avoid the higher penalty.
Source: Optima Tax Relief
Get briefs like this tuned to your business.
In the app, Founder Briefs are personalized to your country, industry and stage, and you can save the ones that matter.
Related updates
More that helps you.
Ontario cuts small-business corporate tax rate to 2.2% on July 1, 2026
Ontario's 2026 budget lowers the small-business corporate income tax rate for Canadian-controlled private corporations (CCPCs) from 3.2% to 2.2%, effective July 1, 2026, prorated f…
$20,000 instant asset write-off to become permanent from 1 July 2026
In the 2026-27 Budget (announced 12 May 2026) the Australian Government said it will permanently set the small business instant asset write-off at $20,000 from 1 July 2026. Small b…
UK employer NIC stays 15% on a £5,000 threshold for 2026/27; Employment Allowance £10,500
For the 2026/27 tax year (from 6 April 2026), employer Class 1 National Insurance remains at 15% and the secondary threshold at which it becomes payable stays at £5,000 per year, c…
Provisional tax kicks in above $5,000 RIT; UOMI at 10.96% for 2026-27
The taxpayer's paying (underpayment) UOMI rate is 8.97% p.a. effective 16 January 2026 (down from 9.89%), not 10.96%. Best phrased as 'currently 8.97%, set by Order in Council and…
Keep exploring
Related across the site
ToolGustoGusto runs full-service payroll for US businesses, handling paychecks, tax filing, and direct deposit, plus benefits, onboarding, and contractor payments. It automates federal, state, and local payroll tax compliance.ToolFreshBooksFreshBooks is cloud accounting and invoicing software aimed at freelancers and service-based small businesses, with strong time tracking, expenses, and client billing.ToolQuickBooksCloud accounting software for tracking income and expenses, invoicing, and preparing for taxes.Term409A ValuationAn independent appraisal of a private company's common stock, used to set the strike price for employee stock options in the US.AI advisorLedger LenaBookkeeping & back officeAI advisorTax MarcusPractical tax, bookkeeping & compliance