Trading costs, spreads and commissions explained

Buying and selling investments carries costs even when the account statement lists no fee. Some costs are explicit, such as a commission charged per trade. Others are built into the price, such as the gap between the price a buyer pays and the price a seller receives. A new investor who understands both kinds can estimate what a trade will really cost before placing it.

The principle stays the same even as broker pricing varies: every trade has a cost somewhere.

Commissions and other explicit charges

A commission is a fee a broker charges for executing a trade. Many online brokers have removed commissions on trades in U.S.-listed stocks and exchange-traded funds, but that does not make trading free. Options contracts often carry a per-contract charge, some mutual fund purchases may carry fees, and certain accounts or services charge maintenance or transfer fees. Read the broker's published fee schedule before assuming a trade has no explicit cost.

Explicit charges are only part of the picture. Small regulatory fees, transfer fees and currency conversion charges can appear on statements too, particularly when buying investments denominated in another currency. The applicable list depends on the account and the type of investment, which is why the same trade can carry different charges at different brokers.

In the United States, commissions paid on a purchase generally add to the investment's cost basis, which reduces the taxable gain when you sell. Keep trade confirmations so you can match those amounts later.

Bid-ask spreads you pay on every trade

The bid is the highest price a buyer is offering, and the ask is the lowest price a seller will accept. The difference between them is the spread. Suppose a share is quoted with a bid of $49.95 and an ask of $50.05. Buying at the ask costs $50.05 a share. Selling immediately at the bid would bring in $49.95, so the round trip costs $0.10 a share, or about 0.2 percent of the price, before any price movement.

Spreads vary. Heavily traded large companies and major funds often have narrow spreads, while thinly traded securities, some small companies and many individual bonds can have wider ones. Spreads also tend to widen in fast-moving or thinly traded markets, when fewer buyers and sellers are quoting prices. Bond dealers also build their markups and markdowns into the price rather than charging them separately, which makes that cost less visible.

Mutual fund shares work differently. They are bought and sold at the net asset value calculated after the market closes, so there is no bid and ask to quote, although a sales load or redemption fee may still apply. Stocks and exchange-traded funds trade on an exchange at quoted prices, so the spread applies to them.

How order types affect the price you get

The order type determines how a trade is executed. A market order asks for an immediate fill at the best available price. In a liquid market that is usually a sensible outcome, but the final price can differ from the last quote, especially when prices move quickly or the market is thin. A limit order sets a maximum price for a purchase or a minimum price for a sale. It protects the price but may not fill if the market never reaches it.

A stop order becomes a market order once the price reaches a specified level, so the fill can land well away from that trigger during a fast decline. A stop-limit order caps the fill price but can fail to execute at all if the price jumps past the limit. For investors who hold for years, these details matter less. Check how your broker describes each order type before using it.

Trading outside regular market hours adds another layer. Extended-hours sessions usually attract fewer participants, so spreads can be wider and prices less predictable. Some brokers accept only limit orders in those sessions, which is one reason to check the rules before placing an after-hours trade.

How frequent trading adds up

Consider the costs of one round trip: the spread, any commission or per-trade fee and possibly a tax on any gain. In the United States, gains on investments held for one year or less are generally taxed at ordinary income rates, which are usually higher than the rates that apply to longer holdings. Each trade therefore carries visible and hidden costs that can reduce the return from the investment itself.

A portfolio that turns over often pays these costs many times a year. Even when each charge is small, the total can become large relative to the returns the trading was meant to produce. That is why investors who trade frequently should track the total cost of their activity, not just the commission. Longer holding periods reduce the number of transactions and the number of times a spread is paid, which is one reason many long-term plans rely on fewer trades.

Trading costs are easy to ignore because each one looks small. Writing down the spread, fees and possible tax before placing a trade turns a series of small charges into a clear figure you can weigh against the reason for the trade. For questions about tax treatment in your own situation, a tax professional is the right resource.