Prerequisite: Spread, commission and execution costs
On a small screen, scroll the figure sideways or open it full size.
Read the figure
An immediate one-unit buy at ask and sell at bid loses 0.20 before commission if quotes do not change.
Learning objective
Explain why a chart and an executable price may differ.
Bid is the quoted selling side and ask the buying side; ask−bid is the spread. A chart may use bid, ask, midpoint or last-traded data. The plotted line alone is insufficient to reconstruct both sides of an executable quote.
With a spread-based quote, a long normally opens at ask and closes at bid, while a short opens at bid and closes at ask. Stop triggering follows the broker’s contract and order rules. A visible bid candle may not display the ask that affected a short.
Provider, timezone and session cut-off can also change OHLC values. Compare matching timestamps and quote types before calling a discrepancy a platform error. Use execution reports and available tick data when reviewing a disputed fill.
Worked example
At bid 100.00 and ask 100.20, an immediate buy and sell of one unit loses 0.20 before commission if quotes do not change. A midpoint chart at 100.10 hides this round-trip spread.
Common mistakes
Do not test executions using midpoint candles with zero spread by accident.
Practice
Record bid and ask alongside a demo order and reconcile them with the chart type.
Sources & further reading
- MetaTrader 5 — Market Watch and symbol specifications
- CFTC — Eight Things You Should Know Before Trading Forex
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My learning pathEditorial review: 15 October 2026 · AI-assisted technical review; independent specialist review pending.
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