Post-Only and Reduce-Only Orders
A post-only order is a limit order that is cancelled instead of executed if it would trade immediately, so it only ever adds liquidity (and usually pays maker fees). A reduce-only order can only shrink an existing position, never increase or reverse it — useful for stops and targets on derivatives exchanges.
Post-only and reduce-only are flags you add to an order, mostly on crypto and derivatives venues. Post-only makes sure a limit order rests in the book instead of trading at once. Reduce-only makes sure an order can only shrink a position. Each venue defines them in its own rules.
- Category
- Order Types
- Reading time
- 3 min
- Also called
- Maker-only order, Close-only order
- Updated
The two flags in plain words
A post-only order won't execute if its limit price would match an existing order straight away.1
A reduce-only order can shrink an existing position but can never make it bigger.2
Placing limit orders as post-only guarantees you pay the maker fee rather than the taker fee.1
How to use them
Choose a limit price
Both flags are usually added to limit orders.
Add post-only
Choose post-only when you want your order to rest on the book and never take liquidity.2
Expect cancels
Expect the order to be rejected or cancelled if it would match immediately.1
Add reduce-only to exits
Use reduce-only for exits, so the order can only cut an open position, not open a new one.1
Use for risk
Use it to keep risk and position size under control.2
Check fills
Confirm the order rested or reduced as expected.
Worked examples
Example 1 — Fee saved
+3.00Hypothetical: maker fee 0.02%, taker 0.05%, order value 10,000.
| Taker fee | 5.00 |
| Maker fee | 2.00 |
| Saved | 3.00 |
Because it was post-only, the order rested on the book and paid the maker fee.1
Example 2 — Post-only cancelled
CancelledA hypothetical buy post-only at 101 when the best offer is 100.
| Would trade now | Yes |
| Result | Cancelled |
The price would have matched straight away, so the post-only order didn't execute.1
Example 3 — Reduce-only stop
Flat, not shortHypothetical long 2 contracts; a reduce-only sell for 3 contracts triggers.
| Closed | 2 |
| New short | 0 |
The reduce-only order closed the position but couldn't flip it into a new one.2
Post-only vs reduce-only
| Aspect | Post-only | Reduce-only |
|---|---|---|
| Goal | Always be the maker | Only shrink a position |
| If it would trade now | Cancelled | Can trade |
| Typical market | Spot and derivatives | Derivatives, margin |
| Main benefit | Maker fees | No accidental flip |
Where these flags help
Fees
Lower Trading Fees and Commissions.
Exits
Safe Stop Loss orders.
Perps
Managing Perpetual Futures.
Market making
Like a Market Maker, resting in the Order Book.
Advantages and disadvantages
Advantages
- Post-only locks in maker fees.
- Reduce-only stops accidental flips.
- Useful for automated exits.
Disadvantages
- Post-only may never fill in fast markets.
- Reduce-only may not be on spot markets.
- Names and rules differ by venue.
- Cancelled orders can leave you unhedged.
Going deeper
Read as far as you need. Each level builds on the one before it.
Post-only
Beginner
Post-only means: add to the book or don't trade at all.2
Reduce-only
Intermediate
Reduce-only can only shrink an open position; it never opens a new one.1
Risk control
Advanced
Reduce-only is a risk-control tool for keeping position size in check.2 Venue rules differ, so read each exchange's documentation.
Common mistakes
Post-only at a crossing price
It will cancel.
Forgetting reduce-only on stops
A stop could flip you short.
Assuming every venue has both
Check the docs.
Ignoring the cancel message
Re-place the order if needed.
Check your understanding
Test yourself before moving on. Each answer comes with an explanation.
Key points to remember
- Post-only only adds liquidity.
- It is cancelled if it would trade now.
- Reduce-only can only shrink a position.
- Both are venue features.
- Read each exchange's rules.
Frequently asked questions
Do stock brokers offer post-only?
Can a reduce-only order fill partly?
Is reduce-only a stop?
Further learning
- Trading Fees and Commissions
Maker vs taker.
- Perpetual Futures
Where reduce-only is common.
- Order Book
Resting orders.
- Liquidation
Why size control matters.
Sources
This article is written in our own words. The sources below support the specific facts, rules and figures marked with a number in the text. Links open the original publisher’s page.
- Kraken. Exchange Trading Rules (opens in a new tab) Checked .
- Bybit. Types of Orders Available on Bybit (opens in a new tab) Checked .
Educational content, not financial advice. Examples use hypothetical prices and simplified costs; actual fees, margin rules and regulations vary by broker, market and country. We are not affiliated with any publisher linked above. Last reviewed . Report an error or request a source credit.