Polymarket vs Kalshi

US access: use the actual product rules

Polymarket US's official account guide describes identity verification before deposits or trading and identifies a CFTC-regulated US exchange. The international platform has a separate geographic-restrictions document. Do not use an old international-access statement to infer that no US product exists.

Account approval, location and contract restrictions still need checking for your actual use. A public price page or a research account does not establish trading permission. Our Polymarket US-status guide explains the distinction.

Fees: compare the final quote

Kalshi's fee documentation says charges can differ by market and that some markets have maker fees, charged when a resting order executes. A limit order is not a universal fee exemption.

Polymarket International describes taker fees on certain markets. Polymarket US has its own schedule and product-specific rules. A single zero-fee label or flat per-contract figure cannot describe all three products.

Record the average executable price for your quantity, entry charges, possible exit costs and relevant funding costs. Check the date of the schedule and the role of each fill. Read the Polymarket fee guide and Kalshi fee guide alongside the current official quote.

Liquidity is specific to a contract and size

Compare bid, ask and depth at the same time. Total trading volume, the number of listed questions and current order-book liquidity answer different questions. None establishes that your intended order will fill at the displayed last price.

For an illustrative 100-contract buy, 20 contracts offered at 52¢ and 80 at 55¢ cost $54.40 before charges. The average fill is 54.4¢, not the 52¢ best ask. The slippage calculator lets you model depth with your own inputs.

Match the resolution rule before the price

Two markets can mention the same election, storm or announcement and still have different payout conditions. Check the outcome definition, official source, cutoff timestamp and time zone, cancellation treatment and payout. A price gap between different claims is not evidence of an equivalent-contract opportunity.

The contract-equivalence worksheet helps record those details. Use it before treating two Yes prices as comparable.

APIs and research tools

Identify the product behind the API documentation, its market identifiers and authentication workflow. A token ID from one system is not automatically an identifier for another. Keep order-execution permissions separate from read-only research.

For sampled international prices, try the Polymarket history viewer. For forecasts you assemble independently, use the Brier-score calculator. Neither tool places orders or proves a profitable strategy.

Reporting forms do not establish a tax advantage

A reporting document is not enough to conclude that one platform gives every user favorable tax treatment. Do not use that claim as a reason to choose a venue. Review the records for your product and circumstances separately from this execution comparison.

A practical decision checklist

1. Confirm the product and account eligibility.
2. Identify an exact contract and preserve its resolution rules.
3. Compare executable prices and available depth for a fixed size.
4. Add applicable entry and exit charges.
5. Check settlement and withdrawal conditions.

If an essential detail is missing, leave the comparison unresolved. Our platform decision worksheet provides a table to record it; the apps comparison covers trading and forecasting activities.