{
  "schemaVersion": "vultax-public-research-data-v1",
  "articleUrl": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees",
  "datasets": [
    {
      "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"
      }
    }
  ]
}