The October 2026 book covers September 21 through October 18 — 28 days of Member-Only Savings that span the transition from the September back-to-school and household reset period into the October commercial calendar that the October guide documents: the Halloween Treats Sale (October 22-31), the Holiday Savings Book arrival (approximately October 19), and the beginning of Costco's holiday commercial season. The October 2026 coupon book's commercial character is specific and