What Is FOK (Fill-Or-Kill) Order?
A Fill-Or-Kill order requires the entire requested quantity to fill immediately at the specified price or better. If even one share short, the entire order is cancelled — no partial fills allowed.
FOK is used in block-size institutional trading where partial fills create unwanted residual exposure. Also common in options and futures where partial fills on multi-leg strategies could leave the trader with mismatched legs.
Retail use is uncommon. Most retail orders default to allowing partial fills, which makes FOK a niche tool. When you need FOK in retail, it's almost always for an options spread where unequal leg fills would be a problem.
Related terms
- IOC (Immediate-Or-Cancel) Order — Order that fills any available quantity immediately and cancels the rest.
- GTC (Good-Till-Cancelled) Order — Order that stays active until executed or manually cancelled, typically up to 60-180 days.
- Limit Order — An order to buy or sell at a specified price or better — guarantees price, not execution.
- Iceberg Order — Large order split into smaller visible chunks to hide true size.