Break of structure (BOS) meaning: what is a BOS in trading?

What a break of structure is

Every trend is a staircase. A downtrend steps down in lower lows and lower highs: price falls, bounces a little, then falls further than before. The moment it falls further than before, closing below the last low, is the break of structure. Repeat that three or four times and you have a downtrend on the chart.

The term comes from smart money concepts (SMC) and ICT teaching, which uses BOS to describe the trend continuing and CHoCH to describe its first failure. The vocabulary is new; the idea is the oldest one in technical analysis. You do not need to believe any story about institutions to use it, just a consistent way of marking swings.

Why traders care: a BOS tells you which side has control on that timeframe. Many SMC traders only look for setups in the direction of the most recent BOS, and wait for price to pull back toward a zone, such as an order block or a fair value gap, before entering.

How to identify a BOS, step by step

1. Mark the swings. Label each swing high and swing low on one timeframe with a fixed rule.
2. Read the sequence. Lower lows and lower highs mean a downtrend; higher highs and higher lows mean an uptrend.
3. Draw a line from the last swing in the trend's direction. In a downtrend, that is the most recent lower low.
4. Wait for a candle to close beyond it. The close below the line is the bearish BOS. Mark it.
5. Move your reference. The lower high that came just before the break is now the swing that protects the trend. A close above it would be a CHoCH.

In the chart above, GBP/USD falls in three clean steps. Each close below the previous low (1.2722, 1.2690, 1.2654) is a bearish BOS, and each bounce stops below the lower high before it.

Bullish vs bearish BOS, and BOS vs CHoCH

A bullish BOS is a close above the last higher high in an uptrend. A bearish BOS is a close below the last lower low in a downtrend. Both say the same thing: the trend just took another step.

The difference from a change of character is direction. A BOS breaks a swing with the trend; a CHoCH breaks the swing that protected the trend and so goes against it. A typical sequence is several BOS in one direction, one CHoCH, then BOS in the new direction if the turn holds.

Many SMC traders also separate internal structure (the small swings inside a pullback) from swing or external structure (the major highs and lows). A BOS on internal structure inside a larger pullback is a much smaller event than a BOS of a major swing low. Being clear which one you are marking prevents most confusion.

Common mistakes

• Wick breaks. A spike below a low that closes back above it often clears out the stops resting there. That is a liquidity sweep, not a BOS, and it can come right before a move the other way.
• Inconsistent swings. If the rule for what counts as a swing changes from chart to chart, the BOS labels will change too. Write the rule down.
• Chasing the breaking candle. The break often happens on a large candle. Entering at its close puts the stop far away; waiting for a pullback usually gives a tighter one.
• Forgetting the higher timeframe. A bearish BOS on the 15-minute chart inside a daily uptrend is a pullback until the daily chart says otherwise.

To turn BOS into entries, see the order block trading strategy and the ICT trading strategy.