TWM Wiki
TWM - Orders Time in Force
GTC (Good ‘Til Cancelled)
(sometimes shortened to “GTC” instead of “GDC” — double-check your platform, but they mean the same)
- Behavior: Your order sits on the book until it’s either fully filled or you manually cancel it.
- Use Case: When you want to patiently wait for your price without worrying about a time limit.
- Example: Place a buy limit at $50,000 for BTC. It may sit there for hours or days until matched.
IOC (Immediate or Cancel)
- Behavior: The order must be matched immediately against the book.
- Any unfilled portion is cancelled right away.
- Use Case: When you want to take liquidity immediately but don’t want leftover “hanging” orders on the book.
- Example: Place an IOC buy for 10 BTC at $50,000. If only 7 BTC is available, you get 7, and the rest (3) is cancelled instantly.
FOK (Fill or Kill)
- Behavior: Either the entire order is filled immediately at your price (or better), or the whole thing is cancelled.
- Use Case: When you need the full size executed, no partials.
- Example: Place a FOK buy for 10 BTC at $50,000. If only 9.9 BTC is available, you get nothing — order is cancelled.
Post-Only
- Behavior: Ensures your order only adds liquidity (posts on the book).
- If placing it would instantly match against an existing order, the exchange cancels it instead.
- Use Case: For maker orders where you want to avoid taker fees (or earn maker rebates).
- Example: Place a Post-Only buy at $50,000. If the best ask is $50,000, it would match immediately → exchange rejects/cancels it. If you enter at $49,999, it stays on the book.
✅ In short:
- GTC = Stays until filled or cancelled
- IOC = Fill what you can now, cancel the rest
- FOK = Fill all immediately or cancel entirely
- Post-Only = Must rest on the book, never take liquidity
Post-Only is not really a "time in force"
- GTC, IOC, and FOK are time in force instructions (they tell the exchange how long the order should live and under what conditions).
- Post-Only is more of an execution constraint (it tells the exchange how to handle the order when placing it on the book).
So they are in different "categories."
Does Post-Only override the others?
- On most exchanges, yes: if you check Post-Only, the system will ignore IOC/FOK logic because those conflict.
- Post-Only + IOC/FOK makes no sense → IOC/FOK want immediate fills, Post-Only forbids immediate fills.
- So if you try to combine them, the exchange usually rejects the order outright or defaults to Post-Only behavior.
- Post-Only + GTC does make sense → it will sit on the book until filled or cancelled, but never execute immediately.
Typical Exchange Behavior
- Binance / Bybit / OKX: If you enable Post-Only and your price would cause an instant match, the order is cancelled automatically.
- Coinbase Pro: If you tick Post-Only and it conflicts with IOC/FOK, you’ll get an error message saying “Invalid combination.”
✅ In short:
- Post-Only overrides IOC/FOK (or makes the order invalid).
- Post-Only works fine with GTC (most common setup).
What is Reduce-Only?
- Definition: A Reduce-Only order can only decrease or close an existing position.
- If placing it would increase your position size, the exchange cancels or adjusts it.
- Mainly used in derivatives trading (futures, perpetuals, margin).
🔹 How It Works in Practice
- Example 1 (Closing a long):
- You’re long 5 BTC. You place a Reduce-Only sell for 3 BTC.
- → If it executes, your position shrinks to 2 BTC long. ✅
- Example 2 (Conflict):
- You’re long 5 BTC. You place a Reduce-Only buy for 3 BTC.
- → This would increase your long to 8 BTC, which violates Reduce-Only.
- → Exchange rejects or ignores it. ❌
- Example 3 (Closing with exact size):
- You’re short 2 BTC. You place a Reduce-Only buy for 2 BTC.
- → If it fills, position goes to flat (0). ✅
🔹 Why Use It?
- Prevents mistakes where a stop order or TP order accidentally flips your position.
- Useful when running multiple exit orders (e.g., several take-profits) and you don’t want overfills to create a reverse position.
- Common in hedged strategies where risk management requires that certain orders never add exposure.