{
  "schemaVersion": "vultax-public-research-data-v1",
  "articleUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees",
  "datasets": [
    {
      "title": "How often a gap cleared fees",
      "columns": [
        {
          "name": "Market class",
          "unit": null
        },
        {
          "name": "Readings",
          "unit": null
        },
        {
          "name": "Matched outcomes",
          "unit": null
        },
        {
          "name": "Crossed before fees",
          "unit": null
        },
        {
          "name": "Cleared fees at the top",
          "unit": null
        },
        {
          "name": "Cleared fees at depth",
          "unit": null
        },
        {
          "name": "Typical result when it did",
          "unit": null
        }
      ],
      "rows": [
        [
          "NFL, before kickoff",
          "7,518",
          "28",
          "0.0%",
          "0.0%",
          "0.0%",
          "—"
        ],
        [
          "College football, before kickoff",
          "3,220",
          "107",
          "3.4%",
          "0.2%",
          "0.1%",
          "$0.21, once"
        ],
        [
          "Premier League, before kickoff",
          "1,153",
          "6",
          "0.3%",
          "0.0%",
          "0.0%",
          "—"
        ],
        [
          "Midterms",
          "13,440",
          "40",
          "34.3%",
          "11.1%",
          "10.1%",
          "$40.55 on $7,690"
        ],
        [
          "Fed September decision",
          "1,011",
          "3",
          "38.5%",
          "33.3%",
          "33.3%",
          "$714.70 on $325,669"
        ]
      ],
      "measurementContext": "Readings every five minutes, 18:51 UTC 12 September to 22:51 UTC 13 September 2026. Typical result is the median profit after fees, and the median capital both legs required, across readings that cleared. Excludes the cost of capital, transfers and settlement risk.",
      "sources": [
        {
          "label": "Kalshi public trade API — events, markets and order books",
          "url": "https://api.elections.kalshi.com/trade-api/v2/events?series_ticker=KXNFLGAME&with_nested_markets=true",
          "note": "Read every five minutes, 12–13 September 2026, with market rule texts"
        },
        {
          "label": "Polymarket Gamma API — events and markets",
          "url": "https://gamma-api.polymarket.com/events/keyset?closed=false&tag_slug=nfl",
          "note": "Markets, fee schedules and rule texts"
        },
        {
          "label": "Polymarket CLOB — order books",
          "url": "https://clob.polymarket.com/books",
          "note": "Bids and asks read in batches every five minutes"
        },
        {
          "label": "Polymarket — trading fees",
          "url": "https://docs.polymarket.com/trading/fees",
          "note": "Per-category taker rates; read 2026-09-12"
        },
        {
          "label": "Kalshi — fee rounding",
          "url": "https://docs.kalshi.com/getting_started/fee_rounding",
          "note": "Trade fees are rounded up"
        },
        {
          "label": "OddsShopper — Kalshi fees",
          "url": "https://www.oddsshopper.com/articles/prediction-markets/kalshi-fees",
          "note": "Third-party statement of the 0.07 taker coefficient"
        },
        {
          "label": "Vultax: Polymarket vs Kalshi midterm odds",
          "url": "https://vultax.com/research/polymarket-vs-kalshi-midterms-odds-2026",
          "note": "Matched midterm contracts and their rules"
        },
        {
          "label": "Vultax: Polymarket sports and esports markets",
          "url": "https://vultax.com/research/polymarket-sports-and-esports-markets",
          "note": "NFL book depth in the six hours before kickoff"
        },
        {
          "label": "Vultax: Kalshi vs Polymarket",
          "url": "https://vultax.com/research/kalshi-polymarket-open-interest-by-category",
          "note": "The venues compared, and the July reading of matched Fed contracts"
        },
        {
          "label": "Vultax: Is Polymarket legal in the US?",
          "url": "https://vultax.com/research/is-polymarket-legal-in-the-us-2026",
          "note": "Which venue U.S. residents can use"
        }
      ],
      "measurement": {
        "kind": "observed",
        "temporalCoverage": "2026-09-12T18:51Z/2026-09-13T22:51Z",
        "population": "184 matched contract pairs with both order books available",
        "methodology": "As in the chart; medians over readings with a positive result after fees."
      },
      "id": "results-table",
      "kind": "published-table",
      "description": "Vultax matched NFL, college football, Premier League, midterm and Fed contracts on Kalshi and Polymarket and walked both order books every five minutes for 28 hours. Midterm gaps cleared both venues' fees in 10% of readings and a Fed longshot in every one; pre-game sports gaps almost never did.",
      "articleUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees",
      "sectionUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees#results",
      "publishedAt": "2026-09-16",
      "modifiedAt": "2026-09-16",
      "version": "103a16f4e1bfcf4ad767d08902d713ff4b473ae820440bdcd4765563ef8ef9a4",
      "isLive": false,
      "limitations": "Published research snapshots and calculations; these exports do not contain current quotes or live account data. Observation windows and populations are stated in the source captions and methodology. Missing metadata is unknown, not zero. Figures describe public order books read every five minutes over 28 hours in September 2026. Fee estimates use published or reported rates and exclude rounding, transfers, the cost of capital and settlement risk. Not a recommendation to trade, and not financial advice.",
      "downloads": {
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        "csv": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees/data.csv?dataset=results-table"
      }
    },
    {
      "title": "Share of readings where a Kalshi–Polymarket gap existed, and where it paid",
      "columns": [
        {
          "name": "Category",
          "unit": null
        },
        {
          "name": "Cleared both venues' fees at depth",
          "unit": "%"
        },
        {
          "name": "Quotes crossed before fees",
          "unit": "%"
        }
      ],
      "rows": [
        [
          "NFL",
          0,
          0
        ],
        [
          "College football",
          0.1,
          3.4
        ],
        [
          "Premier League",
          0,
          0.3
        ],
        [
          "Midterms",
          10.1,
          34.3
        ],
        [
          "Fed decision",
          33.3,
          38.5
        ]
      ],
      "measurementContext": "Five-minute readings, 12–13 September 2026. Sports before kickoff only.",
      "sources": [
        {
          "label": "Kalshi public trade API — events, markets and order books",
          "url": "https://api.elections.kalshi.com/trade-api/v2/events?series_ticker=KXNFLGAME&with_nested_markets=true",
          "note": "Read every five minutes, 12–13 September 2026, with market rule texts"
        },
        {
          "label": "Polymarket Gamma API — events and markets",
          "url": "https://gamma-api.polymarket.com/events/keyset?closed=false&tag_slug=nfl",
          "note": "Markets, fee schedules and rule texts"
        },
        {
          "label": "Polymarket CLOB — order books",
          "url": "https://clob.polymarket.com/books",
          "note": "Bids and asks read in batches every five minutes"
        },
        {
          "label": "Polymarket — trading fees",
          "url": "https://docs.polymarket.com/trading/fees",
          "note": "Per-category taker rates; read 2026-09-12"
        },
        {
          "label": "Kalshi — fee rounding",
          "url": "https://docs.kalshi.com/getting_started/fee_rounding",
          "note": "Trade fees are rounded up"
        },
        {
          "label": "OddsShopper — Kalshi fees",
          "url": "https://www.oddsshopper.com/articles/prediction-markets/kalshi-fees",
          "note": "Third-party statement of the 0.07 taker coefficient"
        },
        {
          "label": "Vultax: Polymarket vs Kalshi midterm odds",
          "url": "https://vultax.com/research/polymarket-vs-kalshi-midterms-odds-2026",
          "note": "Matched midterm contracts and their rules"
        },
        {
          "label": "Vultax: Polymarket sports and esports markets",
          "url": "https://vultax.com/research/polymarket-sports-and-esports-markets",
          "note": "NFL book depth in the six hours before kickoff"
        },
        {
          "label": "Vultax: Kalshi vs Polymarket",
          "url": "https://vultax.com/research/kalshi-polymarket-open-interest-by-category",
          "note": "The venues compared, and the July reading of matched Fed contracts"
        },
        {
          "label": "Vultax: Is Polymarket legal in the US?",
          "url": "https://vultax.com/research/is-polymarket-legal-in-the-us-2026",
          "note": "Which venue U.S. residents can use"
        }
      ],
      "measurement": {
        "kind": "observed",
        "temporalCoverage": "2026-09-12T18:51Z/2026-09-13T22:51Z",
        "population": "26,342 readings of matched contract pairs with both order books, excluding in-play sports",
        "methodology": "Level-by-level walk of the cheaper venue's Yes asks against the other venue's Yes bids, charging each venue's taker fee per level."
      },
      "id": "results-chart",
      "kind": "published-chart",
      "description": "Vultax matched NFL, college football, Premier League, midterm and Fed contracts on Kalshi and Polymarket and walked both order books every five minutes for 28 hours. Midterm gaps cleared both venues' fees in 10% of readings and a Fed longshot in every one; pre-game sports gaps almost never did.",
      "articleUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees",
      "sectionUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees#results",
      "publishedAt": "2026-09-16",
      "modifiedAt": "2026-09-16",
      "version": "b30eb39ef5f98f3f5adb79fcaa0b387d2d81e6f390324a303fd55a33c4eca08b",
      "isLive": false,
      "limitations": "Published research snapshots and calculations; these exports do not contain current quotes or live account data. Observation windows and populations are stated in the source captions and methodology. Missing metadata is unknown, not zero. Figures describe public order books read every five minutes over 28 hours in September 2026. Fee estimates use published or reported rates and exclude rounding, transfers, the cost of capital and settlement risk. Not a recommendation to trade, and not financial advice.",
      "downloads": {
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        "csv": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees/data.csv?dataset=results-chart"
      }
    },
    {
      "title": "Where a gap actually paid",
      "columns": [
        {
          "name": "Contract",
          "unit": null
        },
        {
          "name": "Readings that cleared",
          "unit": null
        },
        {
          "name": "Median profit after fees",
          "unit": null
        },
        {
          "name": "Median capital needed",
          "unit": null
        },
        {
          "name": "Return on that capital",
          "unit": null
        },
        {
          "name": "Earliest settlement",
          "unit": null
        }
      ],
      "rows": [
        [
          "Senate control — Democrats",
          "100% (336 in a row)",
          "$196.30",
          "$21,478",
          "0.91%",
          "When media call the Senate, from November"
        ],
        [
          "Maine Senate — Republican",
          "100%",
          "$47.37",
          "$7,504",
          "0.63%",
          "When the race is called, from November"
        ],
        [
          "Senate control — Republicans",
          "90.8%",
          "$33.93",
          "$12,190",
          "0.28%",
          "When media call the Senate, from November"
        ],
        [
          "Maine Senate — Democrat",
          "52.4%",
          "$35.26",
          "$5,585",
          "0.63%",
          "When the race is called, from November"
        ],
        [
          "Fed: hike of more than 25 bps",
          "100% (337 in a row)",
          "$714.70",
          "$325,669",
          "0.18%",
          "After the 16 September decision"
        ]
      ],
      "measurementContext": "Readings between 18:51 UTC 12 September and 22:51 UTC 13 September 2026. Two South Dakota pairs also cleared, for less than a dollar. Return is profit over capital for the whole holding period, not annualised.",
      "sources": [
        {
          "label": "Kalshi public trade API — events, markets and order books",
          "url": "https://api.elections.kalshi.com/trade-api/v2/events?series_ticker=KXNFLGAME&with_nested_markets=true",
          "note": "Read every five minutes, 12–13 September 2026, with market rule texts"
        },
        {
          "label": "Polymarket Gamma API — events and markets",
          "url": "https://gamma-api.polymarket.com/events/keyset?closed=false&tag_slug=nfl",
          "note": "Markets, fee schedules and rule texts"
        },
        {
          "label": "Polymarket CLOB — order books",
          "url": "https://clob.polymarket.com/books",
          "note": "Bids and asks read in batches every five minutes"
        },
        {
          "label": "Polymarket — trading fees",
          "url": "https://docs.polymarket.com/trading/fees",
          "note": "Per-category taker rates; read 2026-09-12"
        },
        {
          "label": "Kalshi — fee rounding",
          "url": "https://docs.kalshi.com/getting_started/fee_rounding",
          "note": "Trade fees are rounded up"
        },
        {
          "label": "OddsShopper — Kalshi fees",
          "url": "https://www.oddsshopper.com/articles/prediction-markets/kalshi-fees",
          "note": "Third-party statement of the 0.07 taker coefficient"
        },
        {
          "label": "Vultax: Polymarket vs Kalshi midterm odds",
          "url": "https://vultax.com/research/polymarket-vs-kalshi-midterms-odds-2026",
          "note": "Matched midterm contracts and their rules"
        },
        {
          "label": "Vultax: Polymarket sports and esports markets",
          "url": "https://vultax.com/research/polymarket-sports-and-esports-markets",
          "note": "NFL book depth in the six hours before kickoff"
        },
        {
          "label": "Vultax: Kalshi vs Polymarket",
          "url": "https://vultax.com/research/kalshi-polymarket-open-interest-by-category",
          "note": "The venues compared, and the July reading of matched Fed contracts"
        },
        {
          "label": "Vultax: Is Polymarket legal in the US?",
          "url": "https://vultax.com/research/is-polymarket-legal-in-the-us-2026",
          "note": "Which venue U.S. residents can use"
        }
      ],
      "measurement": {
        "kind": "observed",
        "temporalCoverage": "2026-09-12T18:51Z/2026-09-13T22:51Z",
        "population": "Pairs with at least one reading that cleared fees at depth",
        "methodology": "Medians over each pair's cleared readings."
      },
      "id": "where-it-paid-table",
      "kind": "published-table",
      "description": "Vultax matched NFL, college football, Premier League, midterm and Fed contracts on Kalshi and Polymarket and walked both order books every five minutes for 28 hours. Midterm gaps cleared both venues' fees in 10% of readings and a Fed longshot in every one; pre-game sports gaps almost never did.",
      "articleUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees",
      "sectionUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees#where-it-paid",
      "publishedAt": "2026-09-16",
      "modifiedAt": "2026-09-16",
      "version": "8202d234d7979ea6a9d27cf2fe376fd845fcffcfea5f846513249a17d4ca7a1d",
      "isLive": false,
      "limitations": "Published research snapshots and calculations; these exports do not contain current quotes or live account data. Observation windows and populations are stated in the source captions and methodology. Missing metadata is unknown, not zero. Figures describe public order books read every five minutes over 28 hours in September 2026. Fee estimates use published or reported rates and exclude rounding, transfers, the cost of capital and settlement risk. Not a recommendation to trade, and not financial advice.",
      "downloads": {
        "json": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees/data.json?dataset=where-it-paid-table",
        "csv": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees/data.csv?dataset=where-it-paid-table"
      }
    },
    {
      "title": "The contracts must settle the same way",
      "columns": [
        {
          "name": "",
          "unit": null
        },
        {
          "name": "Kalshi",
          "unit": null
        },
        {
          "name": "Polymarket",
          "unit": null
        }
      ],
      "rows": [
        [
          "NFL tie",
          "Each team resolves to $0.50",
          "Resolves 50–50"
        ],
        [
          "NFL game postponed or cancelled",
          "Stays open if it starts within 48 hours; otherwise settles at a fair price",
          "Stays open until played; cancelled with no make-up game resolves 50–50"
        ],
        [
          "Premier League result",
          "90 minutes plus stoppage time; draw is a \"Tie\" market",
          "90 minutes plus stoppage time; draw is a separate market"
        ],
        [
          "Premier League match cancelled",
          "Settles at a fair price",
          "The draw market resolves Yes"
        ],
        [
          "Fed decision",
          "Buckets for the 16 September meeting, such as \"hike of more than 25 bps\"",
          "Change in the upper bound of the target range, rounded up to the nearest 25 bps"
        ]
      ],
      "measurementContext": "Quoted and summarised from each venue's market rules as published through their APIs on 12–13 September 2026.",
      "sources": [
        {
          "label": "Kalshi public trade API — events, markets and order books",
          "url": "https://api.elections.kalshi.com/trade-api/v2/events?series_ticker=KXNFLGAME&with_nested_markets=true",
          "note": "Read every five minutes, 12–13 September 2026, with market rule texts"
        },
        {
          "label": "Polymarket Gamma API — events and markets",
          "url": "https://gamma-api.polymarket.com/events/keyset?closed=false&tag_slug=nfl",
          "note": "Markets, fee schedules and rule texts"
        },
        {
          "label": "Polymarket CLOB — order books",
          "url": "https://clob.polymarket.com/books",
          "note": "Bids and asks read in batches every five minutes"
        },
        {
          "label": "Polymarket — trading fees",
          "url": "https://docs.polymarket.com/trading/fees",
          "note": "Per-category taker rates; read 2026-09-12"
        },
        {
          "label": "Kalshi — fee rounding",
          "url": "https://docs.kalshi.com/getting_started/fee_rounding",
          "note": "Trade fees are rounded up"
        },
        {
          "label": "OddsShopper — Kalshi fees",
          "url": "https://www.oddsshopper.com/articles/prediction-markets/kalshi-fees",
          "note": "Third-party statement of the 0.07 taker coefficient"
        },
        {
          "label": "Vultax: Polymarket vs Kalshi midterm odds",
          "url": "https://vultax.com/research/polymarket-vs-kalshi-midterms-odds-2026",
          "note": "Matched midterm contracts and their rules"
        },
        {
          "label": "Vultax: Polymarket sports and esports markets",
          "url": "https://vultax.com/research/polymarket-sports-and-esports-markets",
          "note": "NFL book depth in the six hours before kickoff"
        },
        {
          "label": "Vultax: Kalshi vs Polymarket",
          "url": "https://vultax.com/research/kalshi-polymarket-open-interest-by-category",
          "note": "The venues compared, and the July reading of matched Fed contracts"
        },
        {
          "label": "Vultax: Is Polymarket legal in the US?",
          "url": "https://vultax.com/research/is-polymarket-legal-in-the-us-2026",
          "note": "Which venue U.S. residents can use"
        }
      ],
      "measurement": {
        "kind": "reference",
        "temporalCoverage": "2026-09-12/2026-09-13",
        "population": null,
        "methodology": "Kalshi rules_primary and rules_secondary fields; Polymarket market descriptions."
      },
      "id": "rules-table",
      "kind": "published-table",
      "description": "Vultax matched NFL, college football, Premier League, midterm and Fed contracts on Kalshi and Polymarket and walked both order books every five minutes for 28 hours. Midterm gaps cleared both venues' fees in 10% of readings and a Fed longshot in every one; pre-game sports gaps almost never did.",
      "articleUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees",
      "sectionUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees#rules",
      "publishedAt": "2026-09-16",
      "modifiedAt": "2026-09-16",
      "version": "c442b4a8857ef8f9319a5148c508dafcec7daeafc4c279c07e1e76151ee93b16",
      "isLive": false,
      "limitations": "Published research snapshots and calculations; these exports do not contain current quotes or live account data. Observation windows and populations are stated in the source captions and methodology. Missing metadata is unknown, not zero. Figures describe public order books read every five minutes over 28 hours in September 2026. Fee estimates use published or reported rates and exclude rounding, transfers, the cost of capital and settlement risk. Not a recommendation to trade, and not financial advice.",
      "downloads": {
        "json": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees/data.json?dataset=rules-table",
        "csv": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees/data.csv?dataset=rules-table"
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}