A stock is quoted at £49.98 bid and £50.02 ask. Buy and you pay £50.02; sell immediately and you receive £49.98. You have lost four pence per share without the price moving at all.
That is the spread, and it is the most consistently overlooked cost in retail investing — precisely because it never appears as a line item.
What changed in 2026
- Zero-commission trading remained standard. The visible fee stayed gone, and the implicit costs remained.
- Order routing transparency improved. Disclosure of how orders are routed and what execution quality results became more available.
- Fractional shares complicated spreads. Fractional trading introduced its own execution characteristics.
- ETF spread awareness grew. Recognition that a low expense ratio can be undone by a wide spread for frequent traders.
Why the spread exists
Someone must stand ready to buy when you sell and sell when you buy. That party — a market maker — takes on risk and holds inventory, and the spread is their compensation.
The size of the spread reflects how much risk that is:
Liquid securities with constant two-way flow have narrow spreads. The market maker holds inventory briefly and can offload it easily.
Illiquid securities — small companies, niche funds, thinly-traded bonds — have wide spreads. Inventory may be held for a long time at genuine risk.
| Security type |
Typical spread |
Round-trip cost |
| Large index ETF |
Very narrow |
Negligible |
| Major listed company |
Narrow |
Small |
| Small company |
Wider |
Meaningful |
| Niche or thematic ETF |
Wider |
Meaningful |
| Illiquid bond |
Wide |
Substantial |
For a buy-and-hold investor in liquid holdings, the spread is genuinely small. For someone trading frequently, or holding illiquid securities, it is the dominant transaction cost.
Timing affects it
Spreads are not constant through the day.
At the open, price discovery is still happening and spreads are wider. Orders placed at the open frequently execute worse than the same order twenty minutes later.
At the close, spreads can widen again as liquidity thins.
During volatility, spreads widen substantially — exactly when people are most inclined to trade.
For ETFs, the spread also depends on the liquidity of the underlying holdings, which is why an ETF tracking illiquid assets has a wider spread than its trading volume alone suggests.
The practical implication is that avoiding the first and last several minutes of the session, and avoiding trading during obvious turbulence, meaningfully improves execution for no effort.
Limit orders control it
A market order says "execute at whatever price is available". In a liquid security that is fine. In an illiquid one, or during volatility, it can execute considerably worse than the quoted price — particularly for an order larger than what is available at the best price.
A limit order says "execute at this price or better". You control what you pay, at the risk of not executing at all if the price moves away.
For anything other than a small order in a highly liquid security, a limit order set at or near the current quote is the sensible default. It costs nothing and removes the possibility of an unpleasant fill — see limit order vs market order.
The related consideration is order size. The quoted spread applies to a certain quantity; a larger order consumes that and executes progressively worse. Splitting a large order across time reduces that impact.
Common mistakes
- Assuming zero commission means zero cost. The spread and routing remain.
- Market orders on illiquid securities. Unpredictable execution.
- Trading at the open or close. Wider spreads.
- Ignoring spreads when comparing funds. A low expense ratio with a wide spread may cost more for an active trader.
- Frequent trading in wide-spread holdings. The cost compounds per round trip.
- Large market orders. Consume available liquidity and execute worse.
- Not checking the spread before trading something unfamiliar. It is visible in the quote.
FAQ
How much does the spread actually cost me?
As a percentage of the trade, it is the spread divided by the price, paid on each round trip. On a liquid holding that is a rounding error; on an illiquid one it can exceed a year of fund fees in a single round trip.
Does it matter for long-term investing?
Much less. Paid once on purchase and once on eventual sale, spread over years, it is negligible for liquid holdings. It matters for frequent trading and illiquid securities.
How do I see the spread?
Most platforms show bid and ask. The difference is the spread. Checking it before trading something unfamiliar takes seconds.
What about payment for order flow?
Where brokers route orders to market makers for payment, it funds zero commissions and raises questions about execution quality. Disclosure has improved; whether execution is better or worse than alternatives is genuinely debated.
Where to go next
For controlling execution price, read limit order vs market order. For the settlement mechanics after a trade, settlement periods, and for the ongoing costs of holding, portfolio turnover cost.
This is general information, not investment advice.