Price gap explained — what it is and will a stop loss stop it?

A price gap is the difference between the close of one candle and the open of the next — the moment when price jumps from one level to another without trading at any value in between. On the forex market this happens above all on Sunday evening, when quotes resume after the weekend break. That is precisely when the stop loss a beginner trusts so readily can close a position far worse than the plan assumed. Below I explain where gaps come from, why forex has fewer of them than the stock market, and how to limit weekend risk.

What a price gap actually is

A candlestick chart assumes continuity — the end of one candle meets the start of the next. A gap is a break in that continuity. Price closes, say, at 1.0850 and opens at 1.0780, and on the daily chart you can see an empty space between those levels. Nobody traded in that range, because the market was closed or liquidity evaporated in a fraction of a second.

The crucial thing to understand is that a gap is not a quoting error or a platform glitch. It is a faithful reflection of the fact that, when trading resumed, the first real bid and offer sat far from the last known price — the market repriced the currency while nobody was watching. No order can be executed "inside" the gap, because there was no price there.

Why forex has fewer gaps than stocks

Stocks listed on an exchange trade in a narrow window — a Warsaw or New York session runs for roughly eight hours a day. For the remaining dozen-plus hours the company lives its own life: it reports earnings, receives rating changes, reacts to news, and the next morning the opening price reflects everything that happened after the closing bell. That is why gaps on stocks are an everyday event, and morning jumps of several per cent surprise nobody.

The currency market works differently because it trades almost without interruption — from Sunday evening to Friday evening, around the clock, five days a week. Price adjusts smoothly, the Asian session hands the baton to Europe and Europe to the Americas, with no daily "close" to accumulate information. So within a trading week gaps on the major pairs are rare and small; the problem appears once a week, at one specific moment.

The weekend gap — the most common gap in currencies

Forex closes on Friday evening and reopens around 22:00 GMT on Sunday (23:00 CET), when the Wellington and Sydney session starts. During those not-quite-two days the world does not stand still — elections are held, central banks make decisions, conflicts erupt. The catch is that over the weekend there is nowhere to react, so all of that information gets packed into the first Sunday quote. That is why most gaps in currencies are weekend gaps.

In a quiet weekend a gap on EUR/USD is a few, maybe a dozen pips — cosmetic, something most traders will not even notice. The trouble appears when something material falls on a weekend. Recall the Brexit referendum of 23 June 2016: the British pound collapsed by hundreds of pips that night, and the following days only deepened the slide. Anyone holding GBP/USD through that stretch opened their eyes to a rate they had not factored in the day before.

"Gaps are among the most telling signals on a chart. They tell us that something has happened to fundamentally change traders' attitudes toward a given market." — John J. Murphy, Technical Analysis of the Financial Markets, New York Institute of Finance, 1999.

Types of gap and what they signal

Technical analysts divide gaps into several types, and this taxonomy is useful on the currency market too, because each type carries different information about what is happening to the trend.

• A breakaway gap forms when price breaks out of a consolidation or past an important support or resistance level. It signals the start of a new, strong move and usually is not filled quickly.
• A runaway gap appears in the middle of a fast-moving trend and confirms its strength. It is the market saying the move still has fuel.
• An exhaustion gap jumps out at the end of a long move, in euphoria or panic. It often signals that the trend is ending and a reversal is near.
• A common (weekend) gap is the typical small break after a pause in trading, with no deeper trend meaning. Most often it is filled quickly.

On the currency market the vast majority of gaps a retail trader meets are exactly these common, weekend ones. Breakaway and exhaustion gaps show up more on stocks and indices, but after truly large macro events they can appear on currency pairs too.

How a gap hits a stop loss

A stop loss — an automatic order to close a position at a loss — is in most cases a market order set at a specific level. When price touches that level, the order activates and the broker closes the position at the first available market price. Under normal conditions that first price is practically identical to the stop level, the difference being a fraction of a pip.

A gap breaks that mechanism. Imagine Marek holding a long position on EUR/USD opened at 1.0850 with a stop loss set at 1.0820, thirty pips lower. On Sunday at 22:00 GMT the market opens straight at 1.0780. Price did not pass through 1.0820 — it never appeared there at all. The first real price is 1.0780, so that is where the broker closes the position. Instead of the planned thirty pips of loss, Marek loses seventy. The gap between the stop level and the execution price is slippage, and during a gap it can be severe.

This is why "a stop loss always protects your capital" is a myth. A standard stop protects against normal market movement — superbly so in the vast majority of situations — but it does not guarantee the execution price. The mechanism that does guarantee it, even inside a gap, is a guaranteed stop loss, offered by some regulated brokers for an extra fee. I cover how a stop differs from a take profit in the piece on stop loss versus take profit, and the worse-execution mechanism in the article on slippage, with the matching forexmechanics.com glossary entry.

The tendency for gaps to fill

Among traders there is a saying that "gaps always fill". It rests on a real observation: small, ordinary weekend gaps genuinely do get filled fairly often within the first hours or days of trading — price returns to the level from before the break, drawn back by pending orders sitting there. But the word "always" is misleading. Gaps driven by a real, fundamental event — like Brexit or a currency shock — can fail to fill for many months, because the market has repriced the currency for good. Building a strategy on "I will buy towards the gap fill" without a stop loss is a straight path to trouble. The tendency to fill is an interesting statistical regularity, not a rule you can base risk management on.

Black swan: the Swiss franc in 2015

The starkest lesson that a gap can be lethal did not even happen on a weekend. On 15 January 2015, a Thursday morning, the Swiss National Bank (SNB) unexpectedly removed the floor it had held since 2011, which had stopped the Swiss franc from strengthening too far against the euro. Within minutes EUR/CHF collapsed by tens of per cent and liquidity simply vanished.

The consequences were brutal. Brokers had no way to fill protective orders at sensible prices, because in the middle of the move there were no offers at all — exactly as in a gap. Stop losses executed dramatically worse than the levels set, some client accounts went below zero, and several brokerage firms took losses in the hundreds of millions of dollars. For the retail market it was a sobering moment: a protective order is not an impenetrable shield.

Regulatory conclusions followed. Since 2018 the European Securities and Markets Authority (ESMA) has imposed mandatory negative balance protection for retail clients. Today a retail account in a similar event could fall to zero but no further — the broker will not demand a top-up. It is a circuit-breaker against catastrophe, not against loss. The moment a broker forcibly closes a losing position is something I cover in the piece on margin call versus stop out. And it is worth remembering that, according to figures brokers publish at ESMA's instruction, between 74 and 89 per cent of retail accounts lose money on leveraged contracts — gaps being one of the factors feeding that statistic.

What to do tomorrow

1. Check on the chart what your weekends look like. Open the daily chart of EUR/USD or the pair you trade and scroll through the last two or three months. Count how many times the Monday candle opened clearly above or below the Friday close — you will see how frequent and how large the gaps really are.
2. Decide consciously whether you hold positions over the weekend. If you trade short-term, the simplest protection costs nothing: close positions on Friday evening, half an hour before quotes end. You give up part of the move's potential, but you eliminate the risk of the Sunday jump.
3. Ask your broker about a guaranteed stop loss and its cost. If you must hold through the weekend or a major macro event, check whether your broker offers a guaranteed stop and what it charges. It is the only order that genuinely guarantees the execution price inside a gap.
4. Size your position to gap risk, not just stop risk. When calculating position size, assume the stop may execute worse than the level indicates. A smaller position before the weekend is a cheaper policy than a guaranteed stop, against the same scenario. The risk management section of forexmechanics.com walks through position sizing in depth.