Trading Costs Glossary: Spreads, Commissions, Slippage and Funding
Trading costs are the charges and execution losses that separate a market’s quoted price from the result a trader actually receives. They include bid–ask spreads, commissions, slippage, financing, market impact and product-specific charges. A strategy with an attractive gross return can produce a poor net result if the full cost structure is ignored.
This glossary explains how the major trading-cost terms are calculated, where they appear in Forex, equities, futures, funds and leveraged products, and which costs are easiest to overlook. Costs depend on the instrument, broker, venue, order size and time; examples below are illustrative rather than quotations from a current provider.
Trading costs glossary: essential terms
Bid price
The best current displayed price a buyer is prepared to pay for a specified quantity. A seller crossing the market may receive this bid for the first portion, but larger quantities can reach lower levels of liquidity.
Ask price
The best currently displayed offer at which a counterparty is willing to sell a specified quantity. A marketable purchase commonly pays the ask or higher available offers, not the midpoint of the spread.
Bid–ask spread
The difference between the best ask and the best bid, typically measured in price units, ticks, pips or basis points. A narrow quoted spread can coexist with poor liquidity when the displayed quantity is small.
Quoted spread
The spread visible in current best bid and offer quotations. It is an instantaneous measure, not the necessarily realised cost for every order across its full quantity and execution path.
Effective spread
A transaction-cost measure comparing an actual execution price with a contemporaneous reference midpoint, often doubled in academic equity-market conventions. The definition and choice of timestamp must be stated before comparing results.
Realised spread
A measure comparing a dealer’s execution price with a later market midpoint, used in market-microstructure analysis. It may reflect compensation for providing liquidity after subsequent price movements and is not the investor’s all-in cost.
Mid-price
The average of the best bid and offer under a chosen quote source. It can be useful for comparisons, but a midpoint valuation should not be assumed to be immediately executable.
Commission
An explicit charge for executing or arranging a transaction. It may be a fixed amount per order, a rate per share or percentage of notional. Fee schedules can have minimum charges and tiers.
Brokerage fee
A broader term for a cost imposed by an intermediary. It can include trading commissions, account fees, platform services or custody charges, depending on the contract and account type.
Exchange fee
A charge imposed by an exchange or venue for particular order flow, trades or market services. Whether a broker passes it on directly or bundles it with other costs affects the investor’s total expense.
Clearing fee
A fee connected with clearing and post-trade risk processing. It differs from commissions and settlement charges, and its applicability depends on instrument and market structure.
Regulatory charge
A charge associated with applicable legal or market rules, sometimes passed through to the client. Rates and applicability are jurisdiction-specific and should be verified rather than copied from another product.
Stamp duty
A tax that may apply to certain security purchases or transfers under relevant law. The rate, exemptions and taxable instruments depend on jurisdiction; do not assume the same rules across UK and US shares.
Foreign-exchange conversion fee
A charge or markup incurred when funds or trade proceeds are converted between account and instrument currencies. The reference exchange rate and effective markup matter as much as any advertised fixed fee.
Currency spread
The difference between exchange rates used for buying and selling a currency. It is one potential component of currency-conversion cost and should be separated from changes in the currency’s underlying market value.
Slippage
The difference between the execution price and a pre-specified reference price. It can be positive or negative, and its magnitude depends on volatility, routing, market depth, order urgency and the reference chosen.
Market impact
The effect that an order’s own size and urgency can have on transaction prices. Large relative participation in a thin order book can change the market before all required quantity is executed.
Opportunity cost
A cost associated with failing to execute a desired position or doing so after prices move. It matters when evaluating limit orders: a lower explicit transaction cost can come with a missed opportunity or an incomplete hedge.
Implementation shortfall
The difference between hypothetical performance at a decision price and actual performance after execution, including filled quantity and often explicit costs. The exact convention must state how unfilled instructions are treated.
Participation rate
The share of available market trading volume taken by an order or execution programme over a period. Higher participation can raise market impact, although order-book liquidity and volatility also influence the outcome.
Turnover
The amount of trading relative to portfolio value under a specified convention. Frequent portfolio changes compound exposure to commission, spreads, taxes and slippage, even when each transaction appears inexpensive.
Maker fee
A fee structure where orders adding resting liquidity may pay a different rate from orders taking existing liquidity. Some venues offer rebates, but eligibility and total costs depend on actual matching behaviour.
Taker fee
A charge associated with removing available liquidity by crossing the order book. Low displayed commission does not guarantee a low all-in transaction cost when the taker fee and spread are included.
Rebate
A payment or credit related to a particular execution arrangement. Rebates are not a substitute for measuring client execution quality and can create conflicts of interest or routing incentives.
Spread markup
A broker-added spread component above its underlying sourcing or reference quotes. Comparing advertised spread ranges without checking trading hours and market conditions can mislead.
Overnight funding
A charge or credit for maintaining certain leveraged or financed positions across a funding cutoff. The reference rate, markup, notional amount and calculation frequency vary among products.
Swap charge
In retail leveraged FX, a position’s overnight financing adjustment is often labelled a swap or rollover charge. It is not always identical to the economic interbank swap instrument bearing a similar name.
Rollover cost
A financing or transaction effect from extending exposure or moving from an expiring futures contract to another delivery month. In futures, curve-related return and trading fees should be separated.
Expense ratio
A recurring fund cost measure, normally expressed annually as a percentage of assets. It is different from brokerage commission and does not capture all trading costs, taxes or tracking differences.
Tracking difference
The realised return of a fund relative to its stated benchmark over a period. It incorporates various effects including fees, taxes, replication, securities lending and timing; it is not exactly the same as the stated expense ratio.
Borrow fee
A cost of borrowing securities for a short sale, often variable with availability and demand. Hard-to-borrow shares can produce elevated fees or recalls that change the economics of short exposure.
Financing rate
The interest or funding basis applied to borrowed capital or leveraged exposure. The rate may be benchmark-linked, fixed for a period, compounded, or adjusted by a broker margin.
Margin interest
Interest on a borrowing balance in a securities margin account. It differs from initial margin posted to collateralise a futures contract, where collateral and settlement arrangements have different conventions.
Futures tick value
The monetary value of one permitted minimum price increment for a stated number of contracts. It is calculated from contract specifications; treating a price tick as a fixed cash amount across instruments is a serious sizing error.
Cost per unit traded
The sum of relevant costs divided by shares, contracts, notional or another denominator. Always identify the denominator, because a charge of 0.1% of notional is not directly comparable to £1 per contract.
How to calculate the bid–ask spread
Suppose a share has a best bid of £20.00 and a best ask of £20.06. The spread is £0.06 per share, calculated by subtracting bid from ask. Relative to the midpoint of £20.03, this is approximately 0.30%. If a trader could buy 100 shares at £20.06 and immediately sell those same shares at £20.00, the gross difference would be £6 before commissions, taxes and any quote movement. That does not prove every purchase will suffer exactly £6: actual outcomes depend on available depth and timing.
For a foreign-exchange pair, a quote of 1.10000 bid and 1.10015 ask has a spread of 0.00015, conventionally 1.5 pips for a pair quoted to four conventional decimal places. A pip’s cash value depends on the notional position and account-currency conversion. A tight spread quoted at one time cannot be assumed to apply during every major data release or in illiquid trading sessions.
Worked example: total cost of a round-trip trade
Imagine a hypothetical investor buying and later selling 200 shares at a £50 reference price. At the entry the best ask is £50.04; the purchase fills at that offer. At the exit, the relevant reference midpoint is £51.00 but the executable bid is £50.95. The investor pays £2 commission per side, and a further £1 in total is attributed to venue-related fees. The actual gross share profit is 200 × (£50.95 − £50.04) = £182. After £4 commission and £1 other fees, the illustrative net profit is £177, before tax and any currency conversion.
Comparing £177 with a hypothetical midpoint-to-midpoint profit of 200 × (£51.00 − £50.00) = £200 shows £23 of difference. Of this, £18 reflects purchasing above the initial reference and selling below the later reference, while £5 reflects explicit charges. In a real trade, market movement during execution might also enter the calculation. Choose reference timestamps carefully and do not present all of the difference as a simple quoted spread.
Worked example: financing a leveraged position
Suppose a product applies a simplified annualised overnight financing rate of 6% to £10,000 of qualifying notional exposure over seven days, calculated without compounding and using a 365-day convention. The notional financing illustration is £10,000 × 0.06 × 7 / 365, approximately £11.51. This figure ignores any entry or exit spread, broker markup, weekend treatment, variation in rates and instrument-specific cash-flow adjustments.
Importantly, posting £1,000 of margin would not mean that financing must be charged only on £1,000; many products use exposure or another defined reference. Nor is the financing calculation a cap on trading loss. The FCA has highlighted concerns about the transparency and value of overnight funding charges in retail CFDs. Readers should examine actual product documents rather than generalising from a simple example.
Gross return is not net return
When a research report presents a strategy that earns 0.15% on a typical gross transaction, a combined 0.20% round-trip spread and fee burden could eliminate the apparent advantage before other adverse outcomes are considered. Costs should be linked to the actual number of transactions, not divided arbitrarily across calendar days. Frequent trading can magnify small per-order charges into a large annual drag.
Transaction-cost analysis also matters for portfolio rebalancing and passive investing. An ETF’s expense ratio is a recurring fund charge, but dealing spread, broker charges, tracking difference, transaction taxes and currency conversion may influence the investor’s realised result. The appropriate comparison measures the complete path from acquiring exposure to exiting it.
Why execution costs rise in volatile conditions
Price volatility, market-maker inventory limits, uncertainty about fair value and reduced market depth can widen quotes together. Immediately after unexpected economic data, quoted prices may change faster than orders can be processed. A trader using the last traded price as a benchmark may observe a much larger slippage figure than during an ordinary session.
Size also changes the result. A quote with 30 units at the best ask does not provide liquidity for a 3,000-unit buy. The order may sweep progressively higher offers, be split over time or remain unfilled under a price limit. Participation rate, urgency and volatility matter more than advertising language about ‘low spreads’.
How to compare brokers and trading venues fairly
Use the same instrument, currency, order size, trading session and execution urgency. Capture the displayed bid and ask and, where available, the depth supporting the desired quantity. Record commission, minimum charge, tax, conversion costs, financing and account costs. Some pricing arrangements quote a wider spread with no separate commission; others show tight raw spreads and charge explicit commission. These models are only comparable after converting charges into the same units.
Be careful with average spreads advertised without their sampling methodology. News releases, illiquid hours and special trading conditions may be excluded or aggregated in a way that does not match the strategy’s actual trading times. Costs reported on a demo platform are not necessarily equivalent to live fills or broker obligations.
Five frequent trading-cost mistakes
First, assuming ‘commission-free’ means free: spreads, financing, FX conversion and ancillary charges may still apply. Second, using midpoint prices in every backtest: repeated free execution at the midpoint can create fictitious profitability. Third, confusing collateral with cost: margin is security for an exposure, whereas financing and execution charges are separate. Fourth, ignoring partial fills: obtaining a better price for only a fraction of a desired order may leave an incomplete hedge. Fifth, overlooking exits: a complete cost estimate must include the position’s unwinding path.
Transaction costs across currencies and settlement dates
An investor may buy a US-listed asset through a sterling-denominated account and focus only on the displayed share commission. The complete economics also involve converting pounds into dollars, possibly converting proceeds back into pounds, and the possibility of exchange-rate movement while the investment is held. A provider might charge a percentage markup on each conversion, use a reference rate with a spread or settle through a currency balance. These are distinct arrangements and their costs should not be assumed equal.
Timing can introduce further differences. A transaction executed on one date may settle on another under the instrument’s relevant calendar, while fees and financing may be accrued according to broker-specific rules. For positions held over weekends, a quoted overnight rate may use a charging schedule that does not match a simple one-day calculation. Accurate total-cost comparison requires the actual fee schedule, currency conversion policy and treatment of cash balances.
Long-term investors should separate one-off costs from recurring charges. A one-off dealing fee is incurred when a transaction occurs, whereas asset-based platform and fund charges may accumulate throughout the holding period. Neither an impressive low trading commission nor an attractively low fund expense ratio establishes the complete cost without studying the other layers.
Explore related glossary guides
Definitions are most useful when connected to neighbouring concepts. See Trading Glossary A–Z, Trading Order Types, Market Data, Trading Risk Management for complementary market terms, risk considerations and examples.
Frequently asked questions
What is the difference between spread and slippage?
Spread is the contemporaneous gap between bid and ask quotes. Slippage compares an actual fill with a specified expected or reference price. A market order can suffer both an ordinary crossing cost and additional adverse price movement; slippage can occasionally be favourable.
Are wider spreads always evidence of an unfair broker?
No. Spreads can widen for economic reasons including volatility, size and lack of counterparties. However, opaque markups or misleading communications warrant scrutiny. Compare total execution outcomes and disclosed terms, not isolated snapshots.
Is an ETF’s expense ratio the only cost?
No. Investors can incur brokerage commission, bid–ask spread, currency conversion and taxes. The fund may also show tracking differences due to portfolio implementation and other factors.
How do funding costs affect long-held leveraged trades?
Depending on the product, financing may accrue daily on notional or another reference. Even when the underlying price does not move, accumulated costs can materially reduce the result. The actual rate and day-count convention must be verified.
Can market impact be measured exactly in advance?
It is uncertain because other participants, orders and market conditions change dynamically. Historical models can estimate likely costs under assumptions, but they cannot guarantee a particular fill.
Related Education guides
See Market Liquidity Explained, Trading Strategy Backtesting, and Trading Mechanics.
Sources and further verification
For regulatory context, see the FCA’s October 2026 CFD good-and-poor-practice findings and CFD information page. For market vocabulary, refer to the CME Group glossary and the SEC’s investor glossary.
Important notice: This guide provides general education only, not personalised investment advice, broker endorsement or a recommendation to trade. Fees, taxation and regulations can change; always check the terms of your actual product.