A proposed class action lawsuit filed Thursday accuses BitMEX of engineering customer liquidations to seize Bitcoin collateral. The complaint arrived on the same day the crypto derivatives platform announced it would shut down after 11 years of operation.

BKX Services Inc. and David Namdar filed the complaint in the US District Court for the Southern District of New York. They allege losses of a combined 622.66 BTC through forced liquidations , BKX claiming at least 305.81 BTC and Namdar alleging losses exceeding 316.85 BTC. The lawsuit seeks the return of that Bitcoin along with compensatory and punitive damages, and aims to represent US customers who purchased BTC swap products dating back to July 23, 2018.

The plaintiffs allege that BitMEX deliberately built its liquidation engine to profit at customer expense. According to the filing, the exchange allowed users to take on leverage up to 100 times their collateral. When positions were automatically liquidated, collateral was still allegedly worth twice the losses incurred.

BitMEX's internal trading desk had access to private customer information, the complaint claims. That desk could continue executing trades during server freezes that locked ordinary users out of their accounts. The remaining collateral from liquidated positions was swept into the platform's insurance fund, effectively allowing BitMEX to capture the差额, according to the plaintiffs.

BitMEX deliberately developed a system that profited from the liquidations," the plaintiffs alleged in the filing.