Key Highlights

  • Costco (NASDAQ:COST) reported US comparable sales excluding gasoline and currency up 8.0% in September 2026, with total comparable sales up 7.6%, per its monthly sales release.
  • The 8.0% rate accelerated from 5.6% in August, an improvement of 2.4 points in simple arithmetic, which suggests stronger traffic or larger baskets as the new fiscal year began.
  • The release date may be the evening of October 7 and not October 8, so the topics file asks readers to confirm the date before relying on the publication timing.
  • High gasoline prices are a feature of the backdrop, which makes the sales figure excluding gas a cleaner read on shopper Demand for Costco (NASDAQ:COST) core merchandise.

The Numbers

Costco (NASDAQ:COST) reported September 2026 sales results in a monthly release dated around October 7 or 8, 2026. US comparable sales excluding gasoline price changes and currency effects rose 8.0%, and total comparable sales rose 7.6%. In August, the comparable measure excluding gas and currency was 5.6%. The jump of 2.4 points is simple arithmetic on two published numbers. The file labels the information as reported and flags the date, so the release should be checked. Costco reports monthly figures for four-week or five-week periods, which means calendar shifts can influence month-to-month comparisons even when demand is steady. Readers should also note that the file does not give traffic or ticket size, so the drivers of the acceleration are not broken out.

What Drives Comparable Sales

Comparable sales measure Revenue at warehouses open at least a year, and they are driven by traffic, average ticket size and Inflation in goods prices. Excluding gasoline strips out the effect of fuel prices, which have been elevated, with Brent near USD 104 in the topics file. Excluding currency removes foreign exchange swings. A rate of 8.0% is strong for a large retailer and suggests that customers are shifting purchases to value-focused retailers during a period of high interest rates and inflation. Membership fees are another source of Costco (NASDAQ:COST) profit, but the monthly release does not cover them. The company's stock-specific valuation is not discussed in the file, and a strong sales month does not by itself justify any share price level, which depends on expectations already built in.

Risks and What to Watch

One strong month does not make a trend, and calendar timing, price inflation and tariffs can all influence the pattern. A 10-year Treasury Yield near 5.35% and weaker consumer sentiment could slow discretionary spending, while higher prices can inflate sales without increasing volumes. Investors should watch the October sales report, fiscal first-quarter Earnings and membership renewal rates, since those show whether the strength reaches profit. The Federal Reserve meets October 27 and 28, 2026. Costco (NASDAQ:COST) should be compared with other big-box retailers, and the release should be read to see categories and regional detail. The topics file does not give a share price reaction, so the market's view of the data is unknown, and any quote should be checked.

Where Things Stand

Costco's September comparable sales were strong at 8.0% excluding gas and currency, up from 5.6% in August, and total comparable sales were 7.6%. Costco (NASDAQ:COST) shows resilient demand in the data reviewed, although the release date needs confirming. The balance of evidence is positive but limited to one month. The next catalysts are the October sales report, the first-quarter earnings release and consumer spending data.