Costco Wholesale Corp New (COST) SEC Filing 10-K Annual report for the fiscal year ending Sunday, September 3, 2017

Exhibit 99.1

Press Release

COSTCO WHOLESALE CORPORATION REPORTS FOURTH QUARTER AND

FISCAL YEAR 2017 OPERATING RESULTS AND SEPTEMBER SALES RESULTS

ISSAQUAH, Wash., October 5, 2017- Costco Wholesale Corporation (“Costco” or the “Company”) (Nasdaq: COST) today announced its operating results for the

Net sales for the 17-week fourth quarter were $41.36 billion, an increase of 15.8 percent from $35.73 billion in the 16-week fourth quarter of fiscal 2016. Net sales for the 53-week fiscal year were $126.17 billion, an increase of 8.7 percent from $116.07 billion in the 52-week fiscal year of 2016.

The Company today also reported net sales of $12.40 billion for the month of September, the five weeks ended October 1, 2017, an increase of 12.1 percent from $11.06 billion during the similar period last year. (The five-week period this year included the last week of the 53-week fiscal year 2017 ended September 3, 2017).

Comparable sales for the 17-week fourth quarter, the 53-week fiscal year, and the 5-week September retail sales month were as follows:

Comparable sales for these periods excluding the impacts from changes in gasoline prices and foreign exchange were as follows:

Net income for the 17-week fourth quarter was $919 million, or $2.08 per diluted share, compared to $779 million, or $1.77 per diluted share, in the 16-week fourth quarter last year.

Net income for the 53-week fiscal year was $2.68 billion, or $6.08 per diluted share, compared to $2.35 billion, or $5.33 per diluted share, in the 52-week prior year. Net income was positively impacted by an $82 million ($0.19 per diluted share) tax benefit in connection with the third-quarter special cash dividend and other net benefits of approximately $51 million ($0.07 per diluted share after tax) for nonrecurring net legal and other matters.