Costco Wholesale Corporation
MX ˙ BMV ˙ US22160K1051
SecurityMX:COST / Costco Wholesale Corporation
InstitutionFlagship Harbor Advisors, Llc
Latest Disclosed Ownership4,869 shares
Latest Disclosed Value $ 4,852,007
Flagship Harbor Advisors, Llc ownership in COST / Costco Wholesale Corporation

On April 28, 2026 - Flagship Harbor Advisors, Llc filed a 13F-HR form disclosing ownership of 4,869 shares of Costco Wholesale Corporation (MX:COST) valued at $4,852,007 USD as of March 31, 2026. The entity filed a previous 13F-HR on January 21, 2026 disclosing 5,033 shares of Costco Wholesale Corporation. This represents a change in shares of -3.26% during the quarter.

Flagship Harbor Advisors, Llc has a history of taking positions in derivatives of the underlying security (COST) in the form of stock options. The firm currently holds call options representing 0 of underlying shares valued at $0 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Institutional Put/Call Ratios
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In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

MX:COST / Costco Wholesale Corporation Historical Put/Call Ratio
Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date
Effective
Date
Form Security Class ID Avg Price
Paid (Est)
Reported
Shares
ΔShares ΔShares
(%)
Reported
Value
(x1000)
ΔValue
(%)
Alloc
(%)
ΔAlloc ΔAlloc (%) Cost Basis
(x1000)
Unrealized
Gain/Loss
(x1000)
2026-04-28 2026-03-31 13F COSTCO WHOLESALE COM 22160K105 4,869 -164 -3.26 4,852 11.80 0.2134
2026-01-21 2025-12-31 13F COSTCO WHOLESALE Common Stock 22160K105 5,033 -1,823 -26.59 4,340 -31.60 0.2048
2025-11-05 2025-09-30 13F COSTCO WHSL CORP COM 22160K105 6,856 -109 -1.56 6,346 -7.96 0.2761
2025-08-04 2025-06-30 13F COSTCO WHSL CORP COM 22160K105 6,965 -70 -1.00 6,895 3.62 0.3266
2025-04-22 2025-03-31 13F COSTCO WHSL CORP COM 22160K105 7,035 -15 -0.21 6,654 2.99 0.3499
2025-01-21 2024-12-31 13F COSTCO WHSL CORP COM 22160K105 7,050 597 9.25 6,460 12.94 0.3393
2024-10-21 2024-09-30 13F COSTCO WHSL CORP COM 22160K105 6,453 115 1.81 5,721 6.18 0.3142
2025-12-02 2024-06-30 13F COSTCO WHSL CORP COM 22160K105 6,338 -70 -1.09 5,387 14.76 0.3238
2024-04-16 2024-03-31 13F COSTCO WHSL CORP COM 22160K105 6,408 -37 -0.57 4,694 10.34 0.3017
2024-01-10 2023-12-31 13F COSTCO WHSL CORP COM 22160K105 6,445 256 4.14 4,254 21.68 0.3094
2023-10-17 2023-09-30 13F COSTCO WHSL CORP COM 22160K105 6,189 -347 -5.31 3,496 -0.63 0.2908
2023-07-11 2023-06-30 13F COSTCO WHSL CORP COM 22160K105 6,536 67 1.04 3,519 9.46 0.2906
2023-04-12 2023-03-31 13F COSTCO WHSL CORP COM 22160K105 6,469 495 8.29 3,214 17.86 0.3027
2023-01-13 2022-12-31 13F COSTCO WHSL CORP COM 22160K105 5,974 121 2.07 2,727 -1.34 0.2796
2022-10-13 2022-09-30 13F COSTCO WHSL CORP COM 22160K105 5,853 366 6.67 2,764 5.10 0.3206
2022-07-13 2022-06-30 13F COSTCO WHSL CORP COM 22160K105 5,487 1,619 41.86 2,630 18.10 0.2954
2022-04-13 2022-03-31 13F COSTCO WHSL CORP COM 22160K105 3,868 307 8.62 2,227 10.14 0.2146
2022-02-17 2021-12-31 13F/A-1 COSTCO WHSL CORP COM 22160K105 3,561 -722 -16.86 2,022 19.29 0.1914
2022-02-10 2021-12-31 13F COSTCO WHSL CORP COM 22160K105 3,561 -722 2,022 0.1914
2021-11-01 2021-09-30 13F COSTCO WHSL CORP COM 22160K105 4,283 0 0.00 1,695 0.00 0.1821
2021-07-26 2021-06-30 13F COSTCO WHSL CORP COM 22160K105 4,283 160 3.88 1,695 16.66 0.1818
2021-05-03 2021-03-31 13F COSTCO WHSL CORP COM 22160K105 4,123 691 20.13 1,453 12.37 0.1650
2021-02-08 2020-12-31 13F COSTCO WHSL CORP COM 22160K105 3,432 143 4.35 1,293 10.80 0.1603
2020-10-13 2020-09-30 13F COSTCO WHOLESALE Common Stock 22160K105 3,289 -35 -1.05 1,167 15.89 0.1576
2020-07-31 2020-06-30 13F COSTCO WHOLESALE Common Stock 22160K105 3,324 265 8.66 1,007 15.48 0.1478
2020-05-12 2020-03-31 13F COSTCO WHOLESALE Common Stock 22160K105 3,059 -43 -1.39 872 -4.39 0.1744
2020-02-14 2019-12-31 13F COSTCO WHOLESALE Common Stock 22160K105 3,102 23 0.75 912 2.82 0.1597
2019-10-22 2019-09-30 13F COSTCO WHOLESALE Common Stock 22160K105 3,079 221 7.73 887 17.48 0.1738
2019-07-22 2019-06-30 13F COSTCO WHOLESALE Common Stock 22160K105 2,858 -25 -0.87 755 8.17 0.1567
2019-04-15 2019-03-31 13F COSTCO WHOLESALE Common Stock 22160K105 2,883 54 1.91 698 21.18 0.1434
2019-01-26 2018-12-31 13F COSTCO WHOLESALE COM 22160K105 2,829 274 10.72 576 -4.00 0.1400
2018-11-05 2018-09-30 13F COSTCO WHOLESALE Common Stock 22160K105 2,555 504 24.57 600 40.19 0.1113
2018-08-14 2018-06-30 13F COSTCO WHOLESALE Common Stock 22160K105 2,051 145 7.61 428 22.64 0.0857
2018-04-23 2018-03-31 13F COSTCO WHSL CORP COM 22160K105 1,906 -253 -11.72 349 -14.25 0.1038
2018-01-24 2017-12-31 13F COSTCO WHSL CORP COM 22160K105 2,159 384 21.63 407 47.46 0.1170
2017-10-23 2017-09-30 13F COSTCO WHSL CORP COM 22160K105 1,775 141 8.63 276 9.96 0.0895
2017-08-09 2017-06-30 13F COSTCO WHSL CORP COM 22160K105 1,634 218 15.40 251 5.02 0.0871
2017-05-16 2017-03-31 13F COSTCO WHSL CORP COM 22160K105 1,416 -4 -0.28 239 0.00 0.0913
2017-05-15 2016-12-31 13F COSTCO WHSL CORP COM 22160K105 1,420 1,420 239 0.1031
Disclosed Call Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share
Price
Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2020-10-13 2020-09-30 13F COSTCO WHSL Listed Options Call 0 -100.00 0 n/a n/a n/a
2020-07-31 2020-06-30 13F COSTCO WHSL Listed Options Call 1 0 n/a n/a n/a
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.