Prediction market fees and spreads should be compared using the price you can actually execute, the quantity filled at each level, every platform charge, and the likely cost of exiting. A low advertised fee does not make a wide spread or thin order book inexpensive.

Key Takeaways

The bid-ask spread is an implicit trading cost even when no line item is labeled “spread fee.”

Compare fill-weighted execution with the quote seen before submission, not only the last trade.

Include entry, exit, settlement or redemption, funding, and withdrawal charges only when they apply.

Maker/taker labels and fee formulas are platform-specific and can change.

Calculate net outcomes for the intended size instead of comparing marketing claims.

What are prediction market fees and spreads?

An explicit fee is a charge defined by the venue's schedule. The spread is the gap between the highest current bid and lowest current ask. It is not normally posted as a separate debit, yet a person who buys at the ask and immediately sells at the bid realizes that gap before other fees.

CFTC material provides the general event-contract context, but commercial terms belong to each venue.［1］ Kalshi documents its own fees and order book, while Polymarket describes a different fee model.［2］［3］［4］ None should be treated as a permanent industry-wide price list.

Cost component	Where to find it	Common comparison error
Bid-ask spread	Live executable order book	Using last trade or midpoint instead
Trading fee	Current official fee schedule	Applying one market's formula everywhere
Slippage/depth	Quantity at successive price levels	Comparing only the best quote
Exit cost	Expected bid, ask, depth, and fee later	Assuming settlement is the only exit
Funding/withdrawal	Cash, card, bank, wallet, or network terms	Mixing account transfer cost with trade cost
Settlement/redemption	Contract and venue rules	Assuming every venue charges or automates it

How does the bid-ask spread affect a trade?

Suppose the best bid is 46 and the best ask is 50. The displayed midpoint is 48, but a new buyer generally faces 50 and an immediate seller generally faces 46 for the available quantities. The four-point spread is a real hurdle even if the platform charges no explicit trading fee on that transaction.

The last trade may be 49, 55, or hours old. It reports history, not guaranteed liquidity. A rounded “chance” display can also hide the executable sides. Our guide to prediction market odds versus probability focuses on interpretation; for cost analysis, record the actual bid and ask.

Spread changes with liquidity and urgency. Competitive orders can narrow it. Thin markets, fast news, large uncertainty, or few participants can widen it. A small order may fit at the best level while a larger order crosses several levels.

Why does order-book depth change the effective price?

The top quote applies only to the quantity posted there. If two contracts are offered at 50, five at 52, and ten at 55, a buy for twelve contracts cannot be evaluated as twelve times 50. Its fill-weighted average depends on the quantities actually executed at each level.

Use this neutral calculation:

Multiply each execution price by its filled quantity.
Add those execution values.
Divide the execution total by total filled quantity to obtain the fee-exclusive average price.
For the fee-inclusive average, add total entry fees to the execution total first, then divide by total filled quantity. Use the same currency unit for prices and fees.
Keep unfilled quantity separate; it has no entry cost yet.

For a hypothetical 12 contracts with an execution total of 600 units and total entry fees of 6 units, the fee-exclusive average is 50 and the fee-inclusive average is (600 + 6) / 12 = 50.5 units per contract. These are illustrative units, not a venue's prices or fee schedule.

A limit can cap the worst accepted price, but it can also leave the order partially filled. Why a prediction market order is not filling explains how price, size, queue, and status interact.

Which explicit fees belong in the comparison?

Read the official schedule for the exact market, order type, account, and date. A venue may distinguish maker and taker activity, use a formula tied to contract price, waive fees for certain markets, or apply separate funding and withdrawal charges. A protocol may charge through the trade, redemption, or blockchain network.

Create a fee inventory rather than one percentage:

Entry trading fee for the executed order.
Exit trading fee if you plan to close before settlement.
Settlement or redemption fee, only if the rules specify one.
Deposit, card, bank, conversion, or withdrawal charge.
Blockchain network fee paid outside the venue.
Currency conversion spread imposed by a payment provider.

Do not count a charge twice. If the execution ledger already reports the fee-inclusive debit, adding the same line again inflates cost. Conversely, a “zero trading fee” claim says nothing about spread, slippage, payment conversion, or withdrawal.

How do maker and taker fees differ?

A maker order generally adds resting liquidity; a taker order generally executes against existing liquidity. Some venues price those roles differently, but the label is determined by what the order does when processed, not by whether the user clicked “limit” or “market.” A marketable limit can take liquidity immediately.

Check partial fills individually. Part of an order might execute at once while the remainder rests, and a venue's fee record should show how it classified each execution. Never infer the final charge from the order form alone.

Platform documentation and ledger entries should agree. If they do not, save the schedule version, order ID, execution IDs, and arithmetic before contacting support. Avoid publishing account numbers or full transaction histories in a public forum.

How should you calculate entry, exit, and net result?

Start with cash flows, not the headline probability. For a position that is later sold, a basic net calculation is:

net trading result = exit proceeds - entry cost - applicable entry and exit fees - transfer costs

Here, entry cost is the total execution value excluding fees, and exit proceeds also exclude fees. Subtract each applicable fee only once; if you instead use fee-inclusive ledger debits and net credits, do not subtract those embedded fees again.

For a position held through final settlement, use the settlement or redemption amount before charges as proceeds and deduct applicable settlement or redemption charges once. If using an already-net credit, do not deduct those charges again. The terminal contract value is not profit because the entry cost still matters.

Run at least three scenarios:

Scenario	Price input	Why it matters
Enter now	Current ask or bid across intended size	Reveals spread and depth cost
Exit early	Conservative opposite-side depth plus fee	Tests whether liquidity could trap the position
Hold to settlement	Rule-defined terminal value minus applicable charges	Separates payout from net return

Do not assume future liquidity resembles today's order book. The spread can widen near news, close, or dispute. Contract rules also matter because a void or fallback may produce a different cash flow than a normal Yes-or-No settlement.

What evidence should you save before comparing venues?

Fee pages can change. Record the page access date, applicable market, formula, exemptions, and worked example provided by the venue. For an actual trade, keep the order and execution ledger rather than relying on a screenshot of the market card.

Use the same comparison sheet for each venue:

Intended side and quantity.
Best executable levels and available depth.
Fill-weighted price.
Entry and possible exit fee formulas.
Funding, currency, network, redemption, and withdrawal costs.
Settlement and void rules.
Net cash flow under early exit, win, loss, and exceptional settlement.

This method does not tell you whether to trade. It prevents a narrow fee claim from hiding the larger transaction cost. For the contract terms behind the last scenario, review prediction market resolution rules and the basic event-contract explanation.

Summary

Compare executable bid and ask, not last trade or midpoint.
Weight every fill by quantity to measure the real entry or exit price.
Inventory explicit trading, transfer, conversion, network, and redemption charges.
Model both early exit and settlement because liquidity and fees differ.
Preserve fee-schedule versions and execution IDs for reconciliation.

Frequently Asked Questions

Is the spread the same as a trading fee?

No. A fee is an explicit charge; the spread is the gap between executable buying and selling prices. Both can reduce the net result.

Does zero fee mean a trade is free?

No. Spread, slippage, funding, conversion, network, redemption, and withdrawal costs may still apply, depending on the venue and account route.

Why did my average price differ from the best ask?

The best ask may have covered only a small quantity. A larger order can execute across several levels, producing a different fill-weighted average.

Is a limit order always a maker order?

No. A limit that immediately crosses an existing quote takes liquidity for that execution. Any remaining quantity may then rest, subject to venue rules.

Should I compare fees as a percentage or cash amount?

Use both. The formula helps compare structure, while the cash amount at your intended size reveals the practical effect and any minimum or rounding behavior.

Are losing positions charged settlement fees?

That depends on the contract and venue schedule. Do not assume a charge or exemption without checking the current official terms.

How does an early exit change total cost?

It introduces another executable spread, possible slippage, and possibly another fee. It can cost more or less than holding depending on price, depth, and outcome.

Can I know the future spread before entering?

No. You can inspect current depth and test scenarios, but future participation, news, market status, and urgency can change liquidity substantially.

Disclaimer: This article provides general educational information, not financial, investment, trading, tax, or legal advice. Fees, spreads, liquidity, order treatment, and settlement costs vary by platform, market, account, and jurisdiction and may change.

Sources:

CFTC — Prediction Markets — https://www.cftc.gov/LearnandProtect/PredictionMarkets
Kalshi — Fees — https://help.kalshi.com/en/articles/13823805-fees
Kalshi — The Orderbook — https://help.kalshi.com/en/articles/13823828-the-orderbook
Polymarket — Fees — https://docs.polymarket.com/trading/fees

Sources checked 9 September 2026.

Related reading:

Prediction Market Fees and Spreads: What to Compare