WASHINGTON — U.S. inflation accelerated to 3.7% over the 12 months through September 2026, adding to concerns about household affordability, business operating expenses and the outlook for Federal Reserve interest-rate policy.

The Consumer Price Index increased 0.6% in September on a seasonally adjusted monthly basis, compared with a 0.4% increase in August, according to the U.S. Bureau of Labor Statistics. The annual inflation rate rose from 3.4% in August, indicating that price pressures strengthened rather than eased during the month.

Higher gasoline prices played a significant role in the increase. The gasoline index climbed 9.1% in September, accounting for more than half of the monthly rise in the overall consumer price index. The energy index increased 5.2%, while shelter costs rose 0.4%.

The latest figures could complicate financial decisions for households already managing expenses such as rent, transportation, groceries and utilities. When prices increase faster than income, consumers have less money available for discretionary purchases, including dining, travel, entertainment and certain retail products.

Businesses are also confronting the consequences of persistent inflation. Companies may face higher transportation, energy, rent and supplier costs, making it more difficult to protect profit margins. Some businesses can pass part of these increases on to customers, while others may have to absorb the additional expenses or adjust staffing and investment plans.

Small businesses can be particularly exposed because they often have less negotiating power with suppliers and fewer financial resources to cushion sudden cost increases. Retailers, restaurants, logistics providers and manufacturers may need to reassess pricing, inventory and operating budgets as expenses change.

The inflation report also matters for the Federal Reserve. Policymakers must balance the need to control price growth against the risk that tighter monetary policy could slow economic activity and hiring. If inflation remains elevated, the central bank may have less flexibility to reduce interest rates. Expectations of higher rates can affect mortgage costs, business loans, credit cards and financing for major purchases.

Core inflation, which excludes food and energy prices, also requires attention because it can provide insight into broader underlying price pressures. The September report showed core consumer prices rising 0.3% monthly and 2.6% annually, suggesting that inflation concerns extend beyond fuel costs alone.

The impact on consumer spending will depend partly on wage growth, household savings and access to credit. Higher-income households may be better able to absorb increased expenses, while families with tighter budgets may reduce nonessential spending or delay large purchases.

For companies, sustained inflation can complicate forecasts and investment decisions. Businesses must estimate whether customers will accept higher prices, whether suppliers will continue raising costs and whether financing expenses will increase further.

Investors will closely monitor upcoming economic releases for signs that price pressures are broadening or beginning to ease. Employment figures, retail sales and additional inflation data could help clarify whether the economy is maintaining momentum despite higher costs.

The September figures do not by themselves determine the Federal Reserve’s next move. However, they reinforce the challenge facing policymakers and businesses as the economy adjusts to higher prices. For households and employers alike, the key question is whether income and revenue growth can keep pace with rising expenses in the months ahead.