Market structure – BOS, CHOCH, Swing High/Low

Introduction

Structure is the skeleton of the chart. Before you identify any demand zone, FVG or Order Block, you have to answer one question: what regime are we in? An uptrend, a downtrend, a consolidation and a change of market character are the foundations of Price Action. Without a correct read of structure, every other concept will be used in the wrong place.

In this lesson you will learn how to mark swing highs and lows objectively, and how to recognise a Break of Structure (BOS) and a Change of Character (CHOCH). That lets you stop guessing and start measuring whether the market is continuing in the same direction or going through a transformation.

Swing High and Swing Low – an operational definition

You need your own written definition. Here is the base definition used at KursTradera.pl – you can modify it, but you have to be consistent.

Swing High (SH): A candle whose high is higher than N candles to the left and N candles to the right. N=2 for intraday, N=3 for swing.

Swing Low (SL): A candle whose low is lower than N candles to the left and N candles to the right.

Swing High definition (N=2):
if High[2] < High[1] and High[1] < High[0] and High[0] > High[1] and High[1] > High[2]
then High[0] = Swing High

Swing Low definition (N=2):
if Low[2] > Low[1] and Low[1] > Low[0] and Low[0] < Low[1] and Low[1] < Low[2]
then Low[0] = Swing Low

Why does this matter? Because if every trader marks swings differently, the BOS will be different too. Write down your N and do not change it while testing a strategy.

Swing hierarchy

Not all swings are equal. We distinguish:

• Minor swing: a short-term turning point inside a correction.
• Major swing: a turning point that breaks the previous major swing in the opposite direction.

Only major swings define a trend. Minor swings are noise inside the structure.

A trend defined by structure

Forget “the trend is your friend” as a slogan. A trend is a sequence.

Uptrend: A sequence of Higher Highs (HH) and Higher Lows (HL). The last HL has not been broken.

Downtrend: A sequence of Lower Lows (LL) and Lower Highs (LH). The last LH has not been broken.

Consolidation / range: No HH/HL or LL/LH sequence. Price prints equal highs and equal lows, and the BOS in either direction is negated.

Uptrend condition (structural):
Previous Swing High < Current Swing High = HH
Previous Swing Low < Current Swing Low = HL
Current low > Previous HL (HL defended)

Downtrend condition (structural):
Previous Swing High > Current Swing High = LH
Previous Swing Low > Current Swing Low = LL
Current high < Previous LH (LH defended)

BOS – Break of Structure

A BOS is a break of a significant swing high or low in the direction of the prevailing trend. It confirms continuation.

Bullish BOS: Price breaks the previous major Swing High. The body closes above it. This shows that buyers are still in control.

Bearish BOS: Price breaks the previous major Swing Low. The body closes below it.

BOS Bullish = Close > Previous Major High + buffer (e.g. 0.1% ATR)
BOS Bearish = Close < Previous Major Low - buffer

The buffer filters out false breakouts of 1 tick. Measure it as a percentage of ATR.

How to use a BOS:

• It is not an entry signal in itself. It is information about the regime.
• After a bullish BOS you look for longs on a correction, not for shorts.
• After a bearish BOS you look for shorts on a correction.

CHOCH – Change of Character

A CHOCH is a break of the structure against the trend. The first signal that the trend may be ending. It differs from a BOS in its direction.

In an uptrend: A bearish CHOCH happens when price breaks the last HL (Higher Low). It means the HH/HL structure has been interrupted.

In a downtrend: A bullish CHOCH happens when price breaks the last LH (Lower High).

A common mistake: calling every breakout a CHOCH. A CHOCH concerns ONLY the last defended swing that held the trend. If in an uptrend we had HL1, HL2, HL3 – a break of HL3 is a CHOCH. A break of a minor low inside the formation between HL2 and HL3 is not a CHOCH.

The procedure for marking structure, step by step

1. Choose a decision timeframe (HTF), e.g. H4, and an execution timeframe (LTF), e.g. M15. You assess the main structure on the HTF.
2. Mark the major swing highs and lows of the last 50-100 candles according to your N definition.
3. Connect them into an HH/HL or LL/LH sequence. Mark the last defended HL/LH.
4. Mark the BOSes in the direction of the trend – that is your continuation map.
5. Wait for a CHOCH – draw an alert line at the last HL/LH. A break = a change of character.
6. After a CHOCH do not flip your position immediately. Wait for a new BOS in the opposite direction to confirm the new trend.

When the plan says do not trade

1. When BOS and CHOCH alternate every 2-3 candles: That is a sign of consolidation/chop. The structure is unreadable. No trend = no directional edge.
2. When the last BOS had a range smaller than 0.5 ATR: A weak BOS = weak continuation. The probability of a false breakout rises. Wait for an impulsive BOS.
3. When the swing definition changes depending on what you want to see: That is cherry-picking. Stop and go back to your written definition.
4. When the CHOCH happened on low volume and without an impulse, and you want to trade the reversal right away: A CHOCH is a warning, not a signal. You need the confirmation of a new BOS.
5. After a major macro event where the structure was destroyed by a gap: Wait until the market builds a new structure. Trading the leftovers of the old structure after an information shock is random.

Mistakes that cost the most

1. Confusing an LTF BOS with an HTF CHOCH. A BOS on M5 does not negate the trend on H4. Always mark which timeframe the structure comes from. Trade in line with the HTF, execute on the LTF.
2. Marking too many minor swings. The chart becomes a spiderweb. Use only major swings for trend decisions. Minor swings serve only to place a more precise stop-loss.
3. No buffer on a BOS/CHOCH. Entering on a breakout 1 tick above the high generates a mass of false signals. Use a body close plus an ATR buffer.
4. Ignoring time. A BOS that formed 30 candles ago matters less than a BOS from the last 5 candles. Structure has a shelf life.
5. Trading a CHOCH as an entry with no plan. Entering only because a CHOCH printed is catching a falling knife. A professional plan: CHOCH -> wait for a correction -> BOS in the new direction -> look for an entry.

A measurable exercise

A task for 20 charts:

1. Take the history of any H1 market, go back 100 candles.
2. Following the N=2 definition, mark the major SH/SL.
3. For each stage determine: trend up/down/range, the last BOS, whether a CHOCH occurred.
4. Write it down in a table:

Metrics:
% of charts where the trend was determined in <30 sec
% of cases where after a BOS the market actually continued at least 1R (measure it)
Number of false CHOCHs (a CHOCH after which there was no BOS in the new direction)

Repeat the exercise after 3 days without looking at your previous answers. Check the consistency of your markings. Consistency >80% means you have an objective definition.

Check yourself

1. What is the difference between a minor and a major swing high?
2. In an uptrend, price breaks the last HH – is that a BOS or a CHOCH? And a break of the last HL?
3. Why do we add an ATR buffer to a BOS?
4. You have an H4 uptrend and a bearish BOS on M15. Does that change the H4 trend? What should you do?
5. Describe the sequence of events: from a CHOCH to the confirmation of a new trend.

Frequently asked questions

How many candles back should I look when marking structure? 50-100 candles on the decision timeframe is enough for day trading and swing trading. Looking further back, you lose context and start trading history rather than the present. Structure has to be current.

Does a BOS have to be on a large body, or is a wick enough? In the Price Action philosophy we wait for a body close beyond the level. A wick on its own is a test of liquidity, not acceptance. A wick that comes back below the level is often a liquidity grab, which we discuss in lesson 4.

What if the CHOCH and the BOS are on the same candle? It happens during strong impulses. For example, price breaks the LH (CHOCH) and immediately the previous HH (BOS) on the same candle. This is a market structure shift with momentum. It is stronger than a plain CHOCH, but it still requires a test on a correction before entry.

Does structure work on M1? Technically, yes. In practice, M1 has a lot of noise and false BOS/CHOCH. If you are starting out, the minimum is M15 as the LTF and H1/H4 as the HTF. The precision of your swing definitions is higher that way.

How do I tell a CHOCH from an ordinary correction? A correction in an uptrend breaks a minor low, but it does not break the last defended major HL. A CHOCH breaks exactly that major HL. The difference is the swing hierarchy. That is why the minor versus major distinction matters so much.

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