Costco Wholesale Corporation
MX ˙ BMV ˙ US22160K1051
SecurityMX:COST / Costco Wholesale Corporation
InstitutionMattern Wealth Management LLC
Latest Disclosed Ownership6,205 shares
Latest Disclosed Value $ 6,183,265
Mattern Wealth Management LLC reports 2.14% increase in ownership of COST / Costco Wholesale Corporation

On April 23, 2026 - Mattern Wealth Management LLC filed a 13F-HR form disclosing ownership of 6,205 shares of Costco Wholesale Corporation (MX:COST) valued at $6,183,265 USD as of March 31, 2026. The entity filed a previous 13F-HR on January 16, 2026 disclosing 6,075 shares of Costco Wholesale Corporation. This represents a change in shares of 2.14% 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.

Upgrade to unlock premium data and export to Excel .

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)
2026-04-23 2026-03-31 13F COSTCO WHOLESALE COM 22160K105 6,205 130 2.14 6,183 18.04 1.2056
2026-01-16 2025-12-31 13F COSTCO WHSL CORP COM 22160K105 6,075 149 2.51 5,238 -4.50 1.0084
2025-10-20 2025-09-30 13F COSTCO WHSL CORP COM 22160K105 5,926 -160 -2.63 5,485 -8.95 1.0950
2025-07-17 2025-06-30 13F COSTCO WHSL CORP COM 22160K105 6,086 167 2.82 6,024 7.61 1.2538
2025-04-23 2025-03-31 13F COSTCO WHSL CORP COM 22160K105 5,919 179 3.12 5,598 6.45 1.2385
2025-01-22 2024-12-31 13F COSTCO WHSL CORP COM 22160K105 5,740 -321 -5.30 5,260 -2.12 1.1601
2024-10-21 2024-09-30 13F COSTCO WHSL CORP COM 22160K105 6,061 105 1.76 5,373 6.14 1.1809
2024-07-17 2024-06-30 13F COSTCO WHSL CORP COM 22160K105 5,956 -231 -3.73 5,062 11.69 1.2170
2024-05-14 2024-03-31 13F COSTCO WHSL CORP COM 22160K105 6,187 -22 -0.35 4,533 10.59 1.1027
2024-02-12 2023-12-31 13F COSTCO WHSL CORP COM 22160K105 6,209 174 2.88 4,099 20.21 1.0537
2023-11-01 2023-09-30 13F COSTCO WHSL CORP COM 22160K105 6,035 337 5.91 3,410 11.15 0.9996
2023-07-26 2023-06-30 13F COSTCO WHSL CORP COM 22160K105 5,698 562 10.94 3,068 20.23 0.8951
2023-05-05 2023-03-31 13F COSTCO WHSL CORP COM 22160K105 5,136 -186 -3.49 2,552 5.02 0.8449
2023-02-06 2022-12-31 13F COSTCO WHSL CORP COM 22160K105 5,322 161 3.12 2,429 -0.33 0.9824
2022-11-01 2022-09-30 13F COSTCO WHSL CORP COM 22160K105 5,161 54 1.06 2,437 -0.45 0.9794
2022-07-25 2022-06-30 13F COSTCO WHSL CORP COM 22160K105 5,107 109 2.18 2,448 -14.94 0.9582
2022-04-14 2022-03-31 13F COSTCO WHSL CORP COM 22160K105 4,998 7 0.14 2,878 1.59 0.9424
2022-01-27 2021-12-31 13F COSTCO WHSL CORP COM 22160K105 4,991 -216 -4.15 2,833 21.07 0.8321
2021-10-13 2021-09-30 13F COSTCO WHSL CORP COM 22160K105 5,207 103 2.02 2,340 11.69 0.7867
2021-07-27 2021-06-30 13F COSTCO WHSL CORP COM 22160K105 5,104 -143 -2.73 2,095 13.30 0.6677
2021-05-13 2021-03-31 13F COSTCO WHSL CORP COM 22160K105 5,247 2,476 89.35 1,849 77.11 0.6517
2021-02-12 2020-12-31 13F COSTCO WHSL CORP COM 22160K105 2,771 94 3.51 1,044 9.89 0.3949
2020-11-12 2020-09-30 13F COSTCO WHSL CORP COM 22160K105 2,677 -10 -0.37 950 16.56 0.4067
2020-07-29 2020-06-30 13F COSTCO WHSL CORP COM 22160K105 2,687 77 2.95 815 9.54 0.3960
2020-05-13 2020-03-31 13F COSTCO WHSL CORP COM 22160K105 2,610 295 12.74 744 9.41 0.5364
2020-02-12 2019-12-31 13F COSTCO WHSL CORP COM 22160K105 2,315 2,315 680 0.4082
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.