Reduce Only on BYDFi, mistakes first: the flipped position, the vanished TP/SL, and the 5% mark-price wall

That sell fills, and since there is no long left to close, it opens a brand-new short at the top of the bounce. The trader thought they were flat. They are not.

On BYDFi futures, the fix is one tick box: Reduce Only. Let's start with the mistakes, because that is where the feature earns its place.

Mistake 1: closing orders that can open positions

A plain limit or conditional order does not know it was meant as an exit. Once the position is gone, it is just a new order. Reduce Only changes that: the order can only reduce an existing position. It will never increase it, and it will never open a new one, so the scenario above cannot flip you short.

How to set it:

• PC: Reduce Only works in one-way position mode. Tick Reduce Only at the upper right of the order block.
• App: on the derivatives page, pick the reduce menu under TP/SL.

Mistake 2: assuming TP/SL survives liquidation

If a position's margin can no longer meet the maintenance requirement, the liquidation engine takes it over. At that point every open order on that contract is canceled, including TP/SL orders and limit orders. After the forced liquidation, any remaining TP/SL orders are batch-canceled. If you check the order history afterwards, those cancellations are expected, not a glitch.

Mistake 3: leaving close orders behind

A close order with no open position behind it is canceled. The same goes for active TP/SL when the position size drops to zero or the direction reverses. When you reduce a position, a reduce order that can no longer be filled in full has its leftover canceled. Example: you place a reduce order, then close most of the position another way. The part of that reduce order that is now bigger than what is left gets canceled.

Mistake 4: pricing past the 5% wall

BYDFi contracts have a 5% price protection band built on the mark price:

• A buy price cannot exceed mark + mark x 5%, which is mark x 1.05.
• A sell price cannot go below mark - mark x 5%, which is mark x 0.95.

If there is no matching counterparty inside that range, the order is canceled.

Worked steps for your own order:

1. Read the mark price on the BTC, ETH, SOL, XRP or DOGE perp you are trading. It is the mark line, not the last trade.
2. Multiply by 1.05 for the highest buy price that can work, or by 0.95 for the lowest sell price.
3. If your panic exit is a sell limit deep below the market to force a fill, check it against the 0.95 line first. Below it, the order is outside the band.
4. Recheck in a fast market. The band moves with the mark, so a level that was inside a minute ago may not be now.

Mistake 5: conditional orders with no margin behind them

A conditional order becomes a live limit or market order when its trigger is hit. If the futures account does not have enough available balance to cover the margin at that moment, the system cancels it. Stops that were set when the account was flush can fail after you move funds or open other trades.

The other cancel reasons, briefly

• You canceled it yourself.
• IOC: whatever does not fill immediately is canceled.
• PostOnly (listed as releasing soon): if it would fill on arrival as a taker, it is canceled.
• Market order: if extreme volatility leaves no counterparty, it can be canceled.

FAQ

Q: Does Reduce Only work in hedge mode? A: On PC it is described for one-way position mode.

Q: Will Reduce Only stop my TP/SL being canceled at liquidation? A: No. Liquidation takeover cancels all orders on that contract.

Q: What is the quickest check after a surprise cancel? A: Match it to the list above. Position gone, margin short, price outside 5% of mark, or the order type's own rules explain most cases.

So before your next exit, ask one question: if the position were already closed, would this order open a new one?