What is a Break of Structure? Definition, Formula, and Example
A break of structure (BOS) is a confirmed close beyond the most recent swing high or low, signaling that the prevailing trend has extended in the same direction.
Break of Structure Definition
A break of structure (BOS) occurs when price closes beyond the most recent significant swing high (in an uptrend) or swing low (in a downtrend), confirming that the existing trend is intact and extending. BOS is the core trend-continuation signal in Smart Money Concepts (SMC) and price-action trading. It is distinct from a change of character (CHoCH), which signals a trend reversal — a BOS confirms the trend you already have, while a CHoCH is the first sign that trend is ending.
How a Break of Structure Is Identified
Identifying BOS requires three steps:
1. Mark the most recent swing high and swing low. A swing high is a candle whose high exceeds the highs of the candles immediately before and after it (the inverse for swing lows).
2. Determine current trend direction. Higher highs and higher lows = uptrend. Lower highs and lower lows = downtrend.
3. Wait for a candle close beyond the relevant swing point. In an uptrend, a candle must *close* above the prior swing high. In a downtrend, a candle must *close* below the prior swing low. Wicks through the level without a body close do not count — that is a liquidity sweep, not a BOS.
The formula is binary: BOS = 1 if Close > PriorSwingHigh (uptrend) or Close < PriorSwingLow (downtrend), else 0. Traders often require the breaking candle to also display displacement — a large body relative to recent average range — to filter weak breaks.
Worked Example
On May 12, 2026, TSLA was in an uptrend on the 1-hour chart, with the most recent swing high at $287.40 set on May 9. Price pulled back to $278.10 on May 11, formed a higher low, and then rallied. At 1:00 PM ET on May 12, TSLA printed a 1-hour candle that closed at $289.85 — a clean close above the $287.40 swing high. That close confirmed the BOS, signaling trend continuation. Over the next two sessions, TSLA extended to $296.20, validating the signal.
When Traders Use a Break of Structure
BOS is used three ways: (1) trend confirmation — only take long entries after a bullish BOS confirms an uptrend is intact; (2) entry trigger — enter on the close of the breaking candle or on a retest of the broken level (former resistance becomes support); (3) stop placement — stops sit below the most recent higher low (or above the most recent lower high in downtrends), giving the trade structure-defined risk. Algorithmic traders use BOS as a filter — many momentum systems require a 1H or 4H BOS before triggering signals on lower timeframes.
Limitations and Common Misconceptions
A BOS confirms the existing trend, but it does not predict how far the trend will extend. Entering on the BOS candle without waiting for a retest often results in chasing — the breaking candle is usually the worst-priced entry in the move. Also, BOS is timeframe-dependent: a 5-minute BOS means little if the 4H trend is opposite. Multi-timeframe alignment is essential. Finally, retail traders frequently confuse a stop-run wick (price spikes above the swing high then immediately reverses) with a BOS — without a body close, no structure has actually broken.