Costco (COST) reports September total same‑store sales up 7.6% YoY and 5.4% MoM.

Costco is among the few large US retailers still reporting monthly same-store sales, a cadence most of the peer set dropped years ago, so these prints function as a recurring read-through on the US consumer between quarterly earnings seasons. Comparable sales in the mid-to-high single digits sit at the strong end of the warehouse club's historical range; the composition matters more than the headline, since traffic-driven gains have historically been received better than ticket-driven ones, and the split between food and discretionary categories has been the cleaner gauge of consumer trade-down behaviour. The MoM figure carries seasonal distortion and typically draws less weight than the YoY line and the two-year stack. Precedent is that single monthly prints move the stock only modestly unless they break a trend, with the bigger reactions reserved for margin commentary and membership fee income at the quarterly report. The follow-ons are the traffic and ticket breakdown, US versus international performance, and any colour on the membership fee, which remains the principal earnings lever and the subject of recurring speculation about an increase.