Buy-Side & Sell-Side Imbalance
Also known as: BISI, SIBI, buy side imbalance sell side inefficiency, sell side imbalance buy side inefficiency
What is it?
BISI and SIBI are the directional names for a three-candle fair value gap. BISI stands for buy-side imbalance, sell-side inefficiency: the gap left behind by an aggressive up-move, where buying was delivered so fast that a stretch of price never traded against sellers. SIBI is the mirror - sell-side imbalance, buy-side inefficiency - left by an aggressive down-move. Both are measured the same way: the space between the first candle's high and the third candle's low for a SIBI, and between the first candle's low and the third candle's high for a BISI. The name tells you which side is missing, and therefore which way the array is expected to work.
The green band is the buy-side imbalance price retraced into and held; the red band above is the sell-side imbalance that capped the next rally 7 pips into it.
A BISI sits below price as a discount area that supports a retrace; a SIBI sits above price as a premium area that caps one. On EUR/USD 15-minute, a rally left candle 1's high at 1.0862 and candle 3's low at 1.0878 - a 16-pip BISI. Price retraced into it two hours later, held at 1.0871 near the midpoint, and continued to 1.0934. A SIBI from the same session, 1.0946 to 1.0958, capped the next rally at 1.0951. The distinction to hold on to is that this is naming, not a separate pattern.
Every BISI and SIBI is a fair value gap; the acronym just states which side of the book was left unfilled, which stops you from treating an array above price as support because you only noticed that it was a gap. Your capital is at risk on any array-based entry. See /risk-warning.
Why it matters: The label states which side of the order flow was left unfilled, so you know whether an inefficiency should support price or cap it before you trade it.
It fixes the direction an inefficiency is expected to work in, which prevents buying an array that is sitting above price as a premium ceiling.
Real-world example
On EUR/USD 15m a 1.0862-1.0878 buy-side imbalance held the retrace at 1.0871 and price ran to 1.0934, while a 1.0946-1.0958 sell-side imbalance capped the next rally at 1.0951.
How SignalBots handles it
SignalBots signals state the direction and the invalidation up front, so you can check whether an alert is working with the imbalance above or below current price rather than inferring it. See /risk-warning.
Pro tip
Read the acronym backwards to place it: the inefficiency half names the missing side, so sell-side inefficiency sits below price and buy-side inefficiency sits above it.
Common pitfalls
Treating every gap as support because most examples are bullish, and buying into a sell-side imbalance that is acting as a premium ceiling.
Frequently asked questions
Is a BISI just a bullish fair value gap?
Yes. The acronym only names which side of the order flow was left unfilled. Every buy-side imbalance is a bullish fair value gap, measured between the first candle's low and the third candle's high.
How do I remember which is which?
The first half names the side that was delivered aggressively and the second names the side that was skipped. Buy-side imbalance means buying was delivered, so the array sits below price and supports it.
Do these arrays have to be filled?
No. Many are never revisited, especially in a strong trend. The imbalance marks where a reaction is likely if price returns, not a level price is obliged to come back to.
Which part of the imbalance do I enter at?
Most traders use the midpoint, the consequent encroachment, as the entry and the far edge as the invalidation. Entering at the near edge fills more often but with a wider stop.
What happens when price closes straight through one?
It inverts. A buy-side imbalance that price closes below becomes a resistance array on the retest, the same way a broken order block becomes a breaker.
Trading involves substantial risk of loss. Historical and backtested results do not guarantee future performance. Read the full risk warning.
