Last Updated: 2026-10-26
A fee percentage without its denominator cannot tell you the cost of a trade. Keep contract quantity, purchase price, cash paid, shares received and fees in separate columns. Then distinguish an early sale from holding through settlement.
Find the applicable schedule
Polymarket's fee documentation, checked October 26, gives a share/price-dependent formula and market-specific parameters. Kalshi's fee schedule includes market multipliers, exceptions and rounding. Neither supports a universal “all trades are free” assumption. Check the exact market and order role; do not substitute a guessed platform-wide percentage.
The fee-formula guide works through an illustrative parameter. A displayed parameter is not automatically a percentage of purchase notional. For a cross-venue comparison, use the same shares, payoff and execution scenario, with each venue's applicable charge. Save the schedule version and the fee shown before submitting an order.
A complete synthetic round trip
Assume buying 100 shares at $0.65 and selling the same 100 at $0.60. Constructed entry and exit fees are $1 and $0.80; these are not provider quotes.
Scroll sideways to see every column. Keyboard: focus the table region and use the arrow keys.
| Cash flow | Amount |
|---|---|
| Purchase | -$65.00 |
| Entry fee | -$1.00 |
| Sale proceeds | +$60.00 |
| Exit fee | -$0.80 |
| Net trade result | -$6.80 |
The price loss alone is $5, or about 7.69% of the $65 purchase. Including these two fees, the loss is $6.80, or about 10.30% of the $66 entry cash. The percentages answer different questions. If the purchase and sale were actual ask/bid fills, subtracting an additional $5 “spread” would double-count that price difference.
Holding the same position through a hypothetical $1 winning settlement instead produces $100 minus the $65 purchase and $1 entry charge: $34 before any other applicable charge. A zero settlement loses $66 under these assumptions. Do not apply the early-sale fee to a settlement unless the actual schedule calls for it.
Funding costs belong to the account path
Record deposit/withdrawal rails, network, conversion, intermediary charges and any required minimum. A venue charging zero for one step does not make the full path free. Fees may already be deducted from the amount received. Reconcile statement cash rather than subtracting the same charge twice.
Suppose the example round trip is the only trade, and separate funding/withdrawal costs total $3. The combined cash result is -$9.80. If that $3 instead supports several trades, keep it as an account-period cost or explain the allocation rule. Assigning the full $3 to every trade would inflate losses.
Do not assume stablecoin balances are risk-free cash or that a self-controlled signing key removes platform access restrictions. Taxes and reporting are a separate jurisdiction-specific question; a platform's CSV is not a tax conclusion.
Turnover and opportunity cost need units
Fifty hypothetical round trips of 100 shares bought at $0.65 and sold at $0.60 create $6,250 of filled notional. That is not a $6,250 starting balance. If the constructed per-round-trip fees remain $1.80, total fees are $90. Actual fees can vary with price, order role, fill grouping and rounding.
An optional benchmark of 4% simple annual return on $66 held for 30 days gives about $0.22 using a 365-day year. This is a chosen comparison, not an available guaranteed yield or a fee charged by the venue. Keep it separate from cash P&L. A probability-point difference cannot be compared directly with a return on capital without the purchase price and payoff model.
Minimum record for a usable estimate
Save the market and token/contract ID, venue/entity, timestamp, quantity, execution prices, cash movements, actual charged fees, role, schedule version and unresolved discrepancies. Record rebates only when earned under the relevant conditions; keep a forecast separate. If a fee parameter or receipt is missing, show an incomplete estimate rather than inventing the missing amount.
Scope and disclosure: Constructed examples, not executed trades, expected returns or tax advice. Official schedules checked October 26, 2026, without funded-account testing. AITR may earn affiliate commissions elsewhere; this worksheet contains no provider referral recommendation.