In order to ensure that our order books are healthy and to prevent unintended price slippage in any market, Poloniex has implemented a price protection mechanism. This rule protects market participants from manipulators or fat finger errors that would have an adverse impact on the order book.

• Any order that would move the price of a particular market by more than 20% (from the best bid or ask) will be rejected with an error code 21356 and error message: Order size would cause too much price movement. Reduce order size.
• The order would need to be broken down into smaller sizes to be accepted by the system. 
• Smart orders are exempted from this rule.

 September 21, 2022