BOS (Break of Structure): a structure break in the direction of the trend

A BOS (break of structure) occurs when price breaks the last significant high in an uptrend or the last significant low in a downtrend, i.e. in line with the existing direction. In ICT/SMC (Inner Circle Trader / Smart Money Concepts), it is regarded as confirmation that the trend is continuing, and a pullback to a zone, for example an order block, is often expected afterward.

The most debated question is what counts as a break: a breach by a wick alone or a candle close beyond the level. A wick breach is sometimes simply a liquidity grab, after which price comes back. A BOS guarantees nothing, because the trend can end right after it. Used on its own, it gives false signals, so it is assessed in the context of a higher timeframe.