What Is a Lock Limit in Futures Trading?
A lock limit is a price boundary set by an exchange beyond which a futures contract is not permitted to trade. Once the price of a futures contract reaches the lock limit — either on the upside or downside — trading in that contract effectively halts for that session, as no orders can be placed or filled beyond that boundary.
How Lock Limits Are Set
Exchanges establish lock limits as a percentage or fixed point movement from the previous session’s settlement price. These limits are determined in advance by the exchange and apply to specific futures products — most commonly agricultural commodities, energy contracts, and financial futures.
| Concept |
Detail |
| Who sets it |
The exchange (e.g. CME Group) |
| When it activates |
Price hits the pre-set maximum move from prior settlement |
| Effect |
No new trades accepted beyond that price level |
| Duration |
Typically applies for the remainder of the trading session |
Lock Limit vs. Circuit Breaker
A lock limit and a circuit breaker both pause trading when markets move too quickly, but they operate differently. A circuit breaker temporarily halts all trading activity on an exchange for a set period before resuming. A lock limit stops price from moving further in one direction but does not halt trading outright — trading at or inside the locked price can still occur if matched orders exist.
What Happens When a Market Locks?
When a futures contract locks limit, traders holding open positions in that contract may find they cannot close or adjust those positions until the next session. This creates a temporary inability to exit — sometimes for multiple consecutive sessions in extreme market events — until the market opens within limit range again.
Lock Limit: What to Keep in Mind
As a precaution, lock limits are most likely to be triggered during periods of extraordinary market stress — supply shocks, geopolitical events, or rapid liquidity withdrawals. Traders active in futures markets should always be aware of the applicable daily price limits for their contracts and factor this into position sizing and contingency planning.
Understand the Rules Before You Trade Futures
Exchange mechanisms like lock limits are designed to protect market integrity, but they also create execution constraints that every futures trader must understand. Create your live VT Markets account or log in now to explore a broad range of tradeable markets.
Risk Warning:Trading CFDs involves significant risk and may not be suitable for all investors. Losses can exceed your initial deposit. Please ensure you fully understand the risks involved before trading.
Back
