Costco Wholesale Corporation
MX ˙ BMV ˙ US22160K1051
SecurityMX:COST / Costco Wholesale Corporation
InstitutionCustom Index Systems, Llc
Latest Disclosed Ownership1,484 shares
Latest Disclosed Value $ 1,478,702
Custom Index Systems, Llc reports 2.05% decrease in ownership of COST / Costco Wholesale Corporation

On May 1, 2026 - Custom Index Systems, Llc filed a 13F-HR/A form disclosing ownership of 1,484 shares of Costco Wholesale Corporation (MX:COST) valued at $1,478,702 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 12, 2026 disclosing 1,515 shares of Costco Wholesale Corporation. This represents a change in shares of -2.05% during the quarter.

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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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)
2026-05-01 2026-03-31 13F/A-1 COSTCO WHOLESALE COM 22160K105 1,484 -31 -2.05 1,479 13.17 0.6441
2026-04-29 2026-03-31 13F COSTCO WHOLESALE COM 22160K105 1,484 -31 1,479 0.6430
2026-02-12 2025-12-31 13F COSTCO WHSL CORP COM 22160K105 1,515 -513 -25.30 1,306 -30.42 0.5769
2025-10-29 2025-09-30 13F COSTCO WHSL CORP COM 22160K105 2,028 443 27.95 1,877 19.63 0.5578
2025-08-13 2025-06-30 13F COSTCO WHSL CORP COM 22160K105 1,585 182 12.97 1,569 18.33 0.7487
2025-05-14 2025-03-31 13F COSTCO WHSL CORP COM 22160K105 1,403 59 4.39 1,327 7.72 0.6727
2025-01-23 2024-12-31 13F COSTCO WHSL CORP COM 22160K105 1,344 34 2.60 1,231 6.03 0.6611
2024-10-24 2024-09-30 13F COSTCO WHSL CORP COM 22160K105 1,310 -377 -22.35 1,161 -18.98 0.6290
2024-08-06 2024-06-30 13F COSTCO WHSL CORP COM 22160K105 1,687 320 23.41 1,434 43.16 0.8233
2024-05-14 2024-03-31 13F COSTCO WHSL CORP COM 22160K105 1,367 571 71.73 1,002 90.67 0.5696
2024-01-26 2023-12-31 13F COSTCO WHSL CORP COM 22160K105 796 796 525 0.3238
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.