# Post Only and Time-in-Force (TIF)

### **Post Only**

An optional setting for limit orders. When enabled, the order is guaranteed to enter the order book as a maker order — it will never match against existing orders on placement. If it would match immediately, it's rejected instead of filled.

Use Post Only when you want to ensure you always pay the maker fee rather than the taker fee.

### **Time-in-Force (TIF)**

Controls how long your order stays active before it's executed or cancelled. Aster supports three types of TIF orders:

| Type                          | Behaviour                                                                              |
| ----------------------------- | -------------------------------------------------------------------------------------- |
| **GTC** (Good 'Til Cancelled) | Stays active until fully filled or manually cancelled.                                 |
| **IOC** (Immediate or Cancel) | Executes immediately, fully or partially. Any unfilled portion is cancelled instantly. |
| **FOK** (Fill or Kill)        | Must fill in full immediately, or the entire order is cancelled. No partial fills.     |

**Note:** Iceberg orders are not supported for IOC or FOK order types.


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