CANTILLON CAPITAL MANAGEMENT LLC: INTERACTIVE BROKERS GROUP IN (IBKR): Quarterly 13F Position History
As of Q2 2026, CANTILLON CAPITAL MANAGEMENT LLC reported 517,833 shares of INTERACTIVE BROKERS GROUP IN (IBKR), worth $45.1M and representing 6.8% of its 13F equity book. Quarter-over-quarter share count change: 10,728,048 (-95.4%) . The position first appeared in Q2 2017 and has been disclosed across 37 13F-HR filings in Pactolio's tracked window.
- 517,833Shares Held (Latest Filing)
- $45.1MReported Market Value (Latest Filing)
- 6.8%Portfolio Weight (% of 13F Equity Book)
- 10,728,048Quarter-over-Quarter Share Change
- -$709.2MQuarter-over-Quarter Value Change
- 12,803,631Peak Reported Shares (Historical)
Quarterly 13F-HR Disclosure History Source: SEC 13F-HR filings, 37 quarter s
| Quarter | Shares | QoQ Share Change | Share Change (%) | Market Value | Weight | Implied Price |
|---|---|---|---|---|---|---|
| Q2 2026 | 517,833 | 10,728,048 | -95.4% | $45.1M | 6.8% | $87.0 |
| Q1 2026 | 11,245,881 | 1,514,023 | -11.9% | $754.3M | 5.0% | $67.1 |
| Q4 2025 | 12,759,904 | +95,878 | +0.8% | $820.6M | 4.4% | $64.3 |
| Q3 2025 | 12,664,026 | 139,605 | -1.1% | $871.4M | 4.8% | $68.8 |
| Q2 2025 | 12,803,631 | +9,509,805 | +288.7% | $709.4M | 4.1% | $55.4 |
| Q1 2025 | 3,293,826 | 101,864 | -3.0% | $545.4M | 3.5% | $165.6 |
| Q4 2024 | 3,395,690 | +18,047 | +0.5% | $599.9M | 3.6% | $176.7 |
| Q3 2024 | 3,377,643 | 100,932 | -2.9% | $470.7M | 2.9% | $139.4 |
| Q2 2024 | 3,478,575 | 177,129 | -4.8% | $426.5M | 2.9% | $122.6 |
| Q1 2024 | 3,655,704 | 73,165 | -2.0% | $408.4M | 2.6% | $111.7 |
| Q4 2023 | 3,728,869 | 90,760 | -2.4% | $309.1M | 2.1% | $82.9 |
| Q3 2023 | 3,819,629 | 14,839 | -0.4% | $330.6M | 2.5% | $86.6 |
| Q2 2023 | 3,834,468 | +230,068 | +6.4% | $318.5M | 2.2% | $83.1 |
| Q1 2023 | 3,604,400 | +384,186 | +11.9% | $297.6M | 2.4% | $82.6 |
| Q4 2022 | 3,220,214 | +749,342 | +30.3% | $233.0M | 2.0% | $72.3 |
| Q3 2022 | 2,470,872 | 22,039 | -0.9% | $157.9M | 1.4% | $63.9 |
| Q2 2022 | 2,492,911 | +268,408 | +12.1% | $137.1M | 1.1% | $55.0 |
| Q1 2022 | 2,224,503 | +62,011 | +2.9% | $146.6M | 1.0% | $65.9 |
| Q4 2021 | 2,162,492 | 163,326 | -7.0% | $171.7M | 1.1% | $79.4 |
| Q3 2021 | 2,325,818 | 33,248 | -1.4% | $145.0M | 1.0% | $62.3 |
| Q2 2021 | 2,359,066 | 38,212 | -1.6% | $155.1M | 1.0% | $65.7 |
| Q1 2021 | 2,397,278 | 81,143 | -3.3% | $175.1M | 1.3% | $73.0 |
| Q4 2020 | 2,478,421 | 10,026 | -0.4% | $151.0M | 1.1% | $60.9 |
| Q3 2020 | 2,488,447 | 25,636 | -1.0% | $120.3M | 1.0% | $48.3 |
| Q2 2020 | 2,514,083 | +18,793 | +0.8% | $105.0M | 0.9% | $41.8 |
| Q1 2020 | 2,495,290 | 7,148 | -0.3% | $107.7M | 1.2% | $43.2 |
| Q4 2019 | 2,502,438 | 52,771 | -2.1% | $116.7M | 1.1% | $46.6 |
| Q3 2019 | 2,555,209 | 18,406 | -0.7% | $137.4M | 1.3% | $53.8 |
| Q2 2019 | 2,573,615 | 45,023 | -1.7% | $139.5M | 1.4% | $54.2 |
| Q1 2019 | 2,618,638 | 20,282 | -0.8% | $135.9M | 1.4% | $51.9 |
| Q4 2018 | 2,638,920 | +23,595 | +0.9% | $144.2M | 1.7% | $54.6 |
| Q3 2018 | 2,615,325 | +141,788 | +5.7% | $144.7M | 1.6% | $55.3 |
| Q2 2018 | 2,473,537 | 67,707 | -2.7% | $159.3M | 1.7% | $64.4 |
| Q1 2018 | 2,541,244 | +501,191 | +24.6% | $170.9M | 1.9% | $67.2 |
| Q4 2017 | 2,040,053 | 105,712 | -4.9% | $120.8M | 1.4% | $59.2 |
| Q3 2017 | 2,145,765 | +219,874 | +11.4% | $96.6M | 1.1% | $45.0 |
| Q2 2017 | 1,925,891 | — | — | $72.1M | 0.9% | $37.4 |
Methodology & FAQ
How This Position History Is Sourced
Each row is one SEC Form 13F-HR filing disclosing this position. Share count, market value, and reported quarter are taken verbatim from the filing; portfolio weight is recomputed against the same filing's total reported equity book. Implied price-per-share is market value divided by shares — a quarter-end mark, not the manager's cost basis. See the full methodology document for the normalization rules.
When did CANTILLON CAPITAL MANAGEMENT LLC first disclose a IBKR position in 13F-HR filings?
CANTILLON CAPITAL MANAGEMENT LLC first reported INTERACTIVE BROKERS GROUP IN (IBKR) on its 13F-HR filing for the period ending 2017-06-30 (Q2 2017). The position has appeared on 37 reported quarters within Pactolio's tracked window.
What was CANTILLON CAPITAL MANAGEMENT LLC's most recent quarter-over-quarter share-count change in IBKR?
Between Q1 2026 and Q2 2026, CANTILLON CAPITAL MANAGEMENT LLC reduced its IBKR position by 10,728,048 shares (-95.4%), leaving 517,833 shares at a market value of $45.1M.
Does the implied price-per-share represent CANTILLON CAPITAL MANAGEMENT LLC's cost basis in IBKR?
No. The implied price-per-share column is the 13F-HR reported market value divided by reported share count on the filing date (end of quarter). It is a quarter-end mark, not a cost basis or transaction price. Use it as a sanity check on the value column, not as an indicator of the manager's entry or exit price.